| Message ID | 1458850962-16057-2-git-send-email-pandit.parav@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
Hello, Parav. Sorry about the delay. > +struct rdma_cgroup { > + struct cgroup_subsys_state css; > + > + /* protects resource pool list */ > + spinlock_t rpool_list_lock; Is this lock still being used? > + /* > + * head to keep track of all resource pools > + * that belongs to this cgroup. > + */ > + struct list_head rpool_head; > +}; > + > +struct rdmacg_pool_info { > + const char **resource_name_table; > + int table_len; It's a bit bothering that resource type defs are outside the controller in a way the controller can't know and assumed to have the same type and range. Architecting kernel code so that allow building modules separately can modify behaviors usually isn't a priority and styling things like this makes implementing specific one-off behaviors cumbersome. It now looks okay but let's say in the future someone wants to use a different type and/or ranges for one of the resources, given the above framework, that person is most likely to blow up pool_info - first with types and min, max values and maybe later with callback handlers and so on, when the only thing which would have been necessary is an one-off handling of that specific setting in the interface functions. Making things modular comes at the cost of complexity and ad-hoc flexiblity. There are cases where such overhead is warranted but as I mentioned before, I don't think this is one of them. Please look back on how this patchset developed. It has been a continuous process of cutting down complexities which didn't need to be there which is the opposite of what we usually want to do - buliding up sophiscation and complexity as necessary from something simple. Please cut down this part too. > +}; > + > +struct rdmacg_device { > + struct rdmacg_pool_info pool_info; > + struct list_head rdmacg_list; > + struct list_head rpool_head; > + /* protects resource pool list */ > + spinlock_t rpool_lock; Does this still need to be a separate lock? > +#define RDMACG_MAX_STR "max" > + > +static DEFINE_MUTEX(dev_mutex); Can you please prefix the above with rdmacg? > +static LIST_HEAD(dev_list_head); Ditto, how about rdmacg_dev_list? > +/* > + * resource pool object which represents per cgroup, per device > + * resources. There are multiple instance of this object per cgroup, ^s > + * therefore it cannot be embedded within rdma_cgroup structure. It > + * is maintained as list. > + */ > +struct rdmacg_resource_pool { > + struct list_head cg_list; > + struct list_head dev_list; Isn't it more conventional to use OBJ_list or OBJs for the head and _node or _link for the members? > +static int > +alloc_cg_rpool(struct rdma_cgroup *cg, struct rdmacg_device *device) > +{ > + struct rdmacg_resource_pool *rpool, *other_rpool; > + struct rdmacg_pool_info *pool_info = &device->pool_info; > + int ret; > + > + rpool = kzalloc(sizeof(*rpool), GFP_KERNEL); > + if (!rpool) { > + ret = -ENOMEM; > + goto err; > + } > + rpool->resources = kcalloc(pool_info->table_len, > + sizeof(*rpool->resources), > + GFP_KERNEL); > + if (!rpool->resources) { > + ret = -ENOMEM; > + goto alloc_err; > + } > + > + rpool->device = device; > + INIT_LIST_HEAD(&rpool->cg_list); > + INIT_LIST_HEAD(&rpool->dev_list); > + spin_lock_init(&device->rpool_lock); > + set_all_resource_max_limit(rpool); > + > + spin_lock(&rpool_list_lock); > + > + other_rpool = find_cg_rpool_locked(cg, device); > + > + /* > + * if other task added resource pool for this device for this cgroup > + * than free up which was recently created and use the one we found. > + */ * It's usually a good idea to have hierarchical objects to be created all the way to the root when a leaf node is requested and link parent at each level. That way, when a descendant object is looked up, the caller can always deref its ->parent pointer till it reaches the top. * Unless it's a very hot path, using a mutex which protects creation of new nodes is usually simpler than doing alloc -> lock -> try-insert. The concurrency in the creation path doesn't matter and even if it mattered it isn't a good idea to bang on allocation path concurrently anyway. > +static void > +uncharge_cg_resource_locked(struct rdma_cgroup *cg, > + struct rdmacg_device *device, > + int index) > +{ > + struct rdmacg_resource_pool *rpool; > + struct rdmacg_pool_info *pool_info = &device->pool_info; > + > + rpool = find_cg_rpool_locked(cg, device); So, with each pool linking to its parent, instead of looking up at each level, it can just follow ->parent recursively. > + /* > + * A negative count (or overflow) is invalid, > + * it indicates a bug in the rdma controller. > + */ > + WARN_ON_ONCE(rpool->resources[index].usage < 0); > + rpool->usage_sum--; What guarantees that this count wouldn't overflow? More on this later. > +/** > + * rdmacg_uncharge_resource - hierarchically uncharge rdma resource count > + * @device: pointer to rdmacg device > + * @index: index of the resource to uncharge in cg in given resource pool > + * @num: the number of rdma resource to uncharge > + * > + */ > +void rdmacg_uncharge(struct rdma_cgroup *cg, > + struct rdmacg_device *device, > + int index) > +{ > + struct rdma_cgroup *p; > + > + spin_lock(&rpool_list_lock); > + for (p = cg; p; p = parent_rdmacg(p)) > + uncharge_cg_resource_locked(p, device, index); > + spin_unlock(&rpool_list_lock); > + > + css_put(&cg->css); Hmm... what css ref is the above putting? > +int rdmacg_try_charge(struct rdma_cgroup **rdmacg, > + struct rdmacg_device *device, > + int index) > +{ ... > + spin_lock(&rpool_list_lock); > + for (p = cg; p; p = parent_rdmacg(p)) { > +retry: > + rpool = find_cg_rpool_locked(p, device); Here, too, you can look up the leaf node once and walk up the hierarhcy. Maybe create a helper, say rdmacg_get_pool_and_lock(), which looks up an existing node or creates all pools from leaf to root and returns with the lock held? ... > +err: > + spin_lock(&rpool_list_lock); > + for (q = cg; q != p; q = parent_rdmacg(q)) > + uncharge_cg_resource_locked(q, device, index); If some resources are not very plentiful and contended, dropping lock before error handling like above could lead to spurious failures. It looks like the above is from trying to create pool at each level while charging up. Creating all necessary pools at the outset should make the code simpler and more robust. > + spin_unlock(&rpool_list_lock); > + css_put(&cg->css); Ditto, where is this from? > +void rdmacg_query_limit(struct rdmacg_device *device, int *limits) > +{ > + struct rdma_cgroup *cg, *p; > + struct rdmacg_resource_pool *rpool; > + struct rdmacg_pool_info *pool_info; > + int i; > + > + pool_info = &device->pool_info; > + > + for (i = 0; i < pool_info->table_len; i++) > + limits[i] = S32_MAX; > + > + cg = get_current_rdmacg(); > + /* > + * Check in hirerchy which pool get the least amount of > + * resource limits. > + */ > + spin_lock(&rpool_list_lock); > + for (p = cg; p; p = parent_rdmacg(p)) { > + rpool = find_cg_rpool_locked(cg, device); Ditto with lookup here. > +static struct rdmacg_device *rdmacg_get_device_locked(const char *name) > +{ > + struct rdmacg_device *device; lockdep_assert_held() would be nice. > + list_for_each_entry(device, &dev_list_head, rdmacg_list) > + if (!strcmp(name, device->name)) > + return device; > + > + return NULL; > +} > + > +static ssize_t rdmacg_resource_set_max(struct kernfs_open_file *of, > + char *buf, size_t nbytes, loff_t off) > +{ > + struct rdma_cgroup *cg = css_rdmacg(of_css(of)); > + const char *dev_name; > + struct rdmacg_resource_pool *rpool; > + struct rdmacg_device *device; > + char *options = strstrip(buf); > + struct rdmacg_pool_info *pool_info; > + u64 enables = 0; > + int *new_limits; > + int i = 0, ret = 0; > + > + /* extract the device name first */ > + dev_name = strsep(&options, " "); > + if (!dev_name) { > + ret = -EINVAL; > + goto err; > + } > + > + /* acquire lock to synchronize with hot plug devices */ > + mutex_lock(&dev_mutex); > + > + device = rdmacg_get_device_locked(dev_name); > + if (!device) { > + ret = -ENODEV; > + goto parse_err; > + } > + > + pool_info = &device->pool_info; > + > + new_limits = kcalloc(pool_info->table_len, sizeof(int), GFP_KERNEL); > + if (!new_limits) { > + ret = -ENOMEM; > + goto parse_err; > + } Hmm... except for new_limits allocation and alloc_cg_rpool() invocation, both of which can be done at the head of the function, nothing seems to require a mutex here. If we move them to the head of the function, can we get rid of dev_mutex entirely? > + ret = rdmacg_parse_limits(options, pool_info, new_limits, &enables); > + if (ret) > + goto opt_err; > + > +retry: > + spin_lock(&rpool_list_lock); > + rpool = find_cg_rpool_locked(cg, device); > + if (!rpool) { > + spin_unlock(&rpool_list_lock); > + ret = alloc_cg_rpool(cg, device); > + if (ret) > + goto opt_err; > + else > + goto retry; > + } > + > + /* now set the new limits of the rpool */ > + while (enables) { > + /* if user set the limit, enables bit is set */ > + if (enables & BIT(i)) { > + enables &= ~BIT(i); > + set_resource_limit(rpool, i, new_limits[i]); > + } > + i++; > + } Maybe we can use for_each_set_bit()? > + if (rpool->usage_sum == 0 && > + rpool->num_max_cnt == pool_info->table_len) { > + /* > + * No user of the rpool and all entries are set to max, so > + * safe to delete this rpool. > + */ > + list_del(&rpool->cg_list); > + spin_unlock(&rpool_list_lock); > + > + free_cg_rpool(rpool); Can't we just count the number of resources which either have !max setting or !0 usage? > +static u32 *get_cg_rpool_values(struct rdma_cgroup *cg, > + struct rdmacg_device *device, > + enum rdmacg_file_type sf_type, > + int count) > +{ > + struct rdmacg_resource_pool *rpool; > + u32 *value_tbl; > + int i, ret; > + > + value_tbl = kcalloc(count, sizeof(u32), GFP_KERNEL); > + if (!value_tbl) { > + ret = -ENOMEM; > + goto err; > + } Do we need this type of interface? Why not let the caller look up the target pool and call this function with pool and resource index? Thanks.
Hi Tejun, On Mon, Apr 4, 2016 at 12:36 PM, Tejun Heo <tj@kernel.org> wrote: > Hello, Parav. > > Sorry about the delay. > Thanks for the review. Comments and answers inline. >> +struct rdma_cgroup { >> + struct cgroup_subsys_state css; >> + >> + /* protects resource pool list */ >> + spinlock_t rpool_list_lock; > > Is this lock still being used? Nop. I should have cleaned this up, as we have the global lock. It must got added in patch recreation time. I will remove it. > >> + /* >> + * head to keep track of all resource pools >> + * that belongs to this cgroup. >> + */ >> + struct list_head rpool_head; >> +}; >> + >> +struct rdmacg_pool_info { >> + const char **resource_name_table; >> + int table_len; > > It's a bit bothering that resource type defs are outside the > controller in a way the controller can't know and assumed to have the > same type and range. Architecting kernel code so that allow building > modules separately can modify behaviors usually isn't a priority and Module cannot really change the behavior just by adding/removing new/old resource type. Behavior is defined by the controller as it does today. > styling things like this makes implementing specific one-off behaviors > cumbersome. I agree that other controllers are not doing this way, for some good reason in those controllers. But its not right to impose the same restriction here. Code is really straight forward where pool_info array length is dynamic, instead of static structure definition. By addressing some of the comments to change from spin lock to mutex, will further reduce the allocation complexity. I believe that should be sufficient. We have discussed advantages this approach in previous patches along with consensus from other rdma experts. In v9 you asked to document them clearly in the Documentation indicating that its alright to define by the module as its done in v9 and v10 patch. > > It now looks okay but let's say in the future someone wants to use a > different type and/or ranges for one of the resources, given the above > framework, that person is most likely to blow up pool_info - first > with types and min, max values and maybe later with callback handlers > and so on, when the only thing which would have been necessary is an > one-off handling of that specific setting in the interface functions. > We can always go back to change the scope of rdma cgroup at that point to restrict for what you have described above. At present thats not the scope and we have reduced the requirements to what is implemented today. Additionally if the min,max setting might arrive for a resource in future, than its likely that it would be applicable to multiple resources than one resource. And in that case putting them inside the pool_info would be appropriate as well. rdma cgroup will have to define the new interface at that point anyway. We have to let this interface be usable first with current coded functionality and flexibility that is not harmful. > Making things modular comes at the cost of complexity and ad-hoc > flexiblity. At this point, complexity of this architecture is not really much. Only overheads are kmalloc and kfree are done on resource pool whose size is decided dynamically instead of a value defined in header file in rdma_cgroup.h. (Instead its in ib_verbs.h) Its fair enough to have that flexibility. > There are cases where such overhead is warranted but as I > mentioned before, I don't think this is one of them. Please look back > on how this patchset developed. It has been a continuous process of > cutting down complexities which didn't need to be there which is the > opposite of what we usually want to do - buliding up sophiscation and > complexity as necessary from something simple. Please cut down this > part too. Tejun, To repeat the basic motivation of this functionality/architecture is: kernel upgrades are done over period of years at customers location. Upgrading kernel for few rdma resources is really silly. Current implementation anyway doesn't let modules define any crazy count either. Currently only 64 different types of resources can be defined anyway. New resource definition anyway goes through reviews by maintainers. So as we talked in past, I would like to continue with this approach. 2nd advantage is, it allows avoiding lot of rework, in bundling kernel modules with different kernel versions. So it is certainly valuable feature with almost nil complexity cost of code or memory that solves two problems with approach. If there two kernel versions with different type of resources and kernel modules with different resources, it gets ugly to maintain that kind of compatibility using compat.h. This approach avoid all such cases. > >> +}; >> + >> +struct rdmacg_device { >> + struct rdmacg_pool_info pool_info; >> + struct list_head rdmacg_list; >> + struct list_head rpool_head; >> + /* protects resource pool list */ >> + spinlock_t rpool_lock; > > Does this still need to be a separate lock? > Nop. I got to remove this. >> +#define RDMACG_MAX_STR "max" >> + >> +static DEFINE_MUTEX(dev_mutex); > > Can you please prefix the above with rdmacg? o.k. I will rename to rdmacg_mutex as I intent to remove all the spin locks and have one mutex lock for all the protections. > >> +static LIST_HEAD(dev_list_head); > > Ditto, how about rdmacg_dev_list? > o.k. >> +/* >> + * resource pool object which represents per cgroup, per device >> + * resources. There are multiple instance of this object per cgroup, > ^s will fix this. >> + * therefore it cannot be embedded within rdma_cgroup structure. It >> + * is maintained as list. >> + */ >> +struct rdmacg_resource_pool { >> + struct list_head cg_list; >> + struct list_head dev_list; > > Isn't it more conventional to use OBJ_list or OBJs for the head and > _node or _link for the members? > _head is more readable than list to me. So I will keep the _head as it is unless this is blocker for patch acceptance. I will replace above two _list items with _node. >> +static int >> +alloc_cg_rpool(struct rdma_cgroup *cg, struct rdmacg_device *device) >> +{ >> + struct rdmacg_resource_pool *rpool, *other_rpool; >> + struct rdmacg_pool_info *pool_info = &device->pool_info; >> + int ret; >> + >> + rpool = kzalloc(sizeof(*rpool), GFP_KERNEL); >> + if (!rpool) { >> + ret = -ENOMEM; >> + goto err; >> + } >> + rpool->resources = kcalloc(pool_info->table_len, >> + sizeof(*rpool->resources), >> + GFP_KERNEL); >> + if (!rpool->resources) { >> + ret = -ENOMEM; >> + goto alloc_err; >> + } >> + >> + rpool->device = device; >> + INIT_LIST_HEAD(&rpool->cg_list); >> + INIT_LIST_HEAD(&rpool->dev_list); >> + spin_lock_init(&device->rpool_lock); >> + set_all_resource_max_limit(rpool); >> + >> + spin_lock(&rpool_list_lock); >> + >> + other_rpool = find_cg_rpool_locked(cg, device); >> + >> + /* >> + * if other task added resource pool for this device for this cgroup >> + * than free up which was recently created and use the one we found. >> + */ > > * It's usually a good idea to have hierarchical objects to be created > all the way to the root when a leaf node is requested and link > parent at each level. That way, when a descendant object is looked > up, the caller can always deref its ->parent pointer till it reaches > the top. This is interesting comment. I cannot recall, but I think its v4 or v5 was exactly doing same. Allocating resource pool first in one loop and charging them in another. In event of failure, uncharging them in 3rd. And you gave comment that time is to move away from that approach for simplicity! That I had refcnt on each object. Anyways, Few things for above comment and some of the below comments. 1. I will replace all the spin lock to single mutex 2. With that it will be, try_charge() will be, - lock() - For multiple levels, until null parent, - allocate() for a given level. - charge for that level. - unlock() 3. uncharge() will be, - lock() - uncharge(), free() if necessary at that level. - unlock() With this spuriousness issue that you described will also be addressed. > > * Unless it's a very hot path, using a mutex which protects creation > of new nodes is usually simpler than doing alloc -> lock -> > try-insert. The concurrency in the creation path doesn't matter and > even if it mattered it isn't a good idea to bang on allocation path > concurrently anyway. > >> +static void >> +uncharge_cg_resource_locked(struct rdma_cgroup *cg, >> + struct rdmacg_device *device, >> + int index) >> +{ >> + struct rdmacg_resource_pool *rpool; >> + struct rdmacg_pool_info *pool_info = &device->pool_info; >> + >> + rpool = find_cg_rpool_locked(cg, device); > > So, with each pool linking to its parent, instead of looking up at > each level, it can just follow ->parent recursively. No. Lookup is being done for the rpool for that device and not the cgroup. doing recursively using ->parent would require additional pointer of rpool type to be maintained which is not necessary because we already have cgroup level parent. Adding ->parent would make it little faster compare to traversing 1 to 4 node entry list. However this is not hot path, so keeping existing code to traverse is more desirable than adding ->parent of rpool type, which also saves memory for large number of cgroup instances. > >> + /* >> + * A negative count (or overflow) is invalid, >> + * it indicates a bug in the rdma controller. >> + */ >> + WARN_ON_ONCE(rpool->resources[index].usage < 0); >> + rpool->usage_sum--; > > What guarantees that this count wouldn't overflow? More on this > later. Are you suggesting to add WARN_ON for usage_sum variable for debugging? I believe 1st warning is sufficient? > >> +/** >> + * rdmacg_uncharge_resource - hierarchically uncharge rdma resource count >> + * @device: pointer to rdmacg device >> + * @index: index of the resource to uncharge in cg in given resource pool >> + * @num: the number of rdma resource to uncharge >> + * >> + */ >> +void rdmacg_uncharge(struct rdma_cgroup *cg, >> + struct rdmacg_device *device, >> + int index) >> +{ >> + struct rdma_cgroup *p; >> + >> + spin_lock(&rpool_list_lock); >> + for (p = cg; p; p = parent_rdmacg(p)) >> + uncharge_cg_resource_locked(p, device, index); >> + spin_unlock(&rpool_list_lock); >> + >> + css_put(&cg->css); > > Hmm... what css ref is the above putting? Its putting the reference which was taken previously during charging time using, get_current_rdmacg() which takes using task_get_css(). > >> +int rdmacg_try_charge(struct rdma_cgroup **rdmacg, >> + struct rdmacg_device *device, >> + int index) >> +{ > ... >> + spin_lock(&rpool_list_lock); >> + for (p = cg; p; p = parent_rdmacg(p)) { >> +retry: >> + rpool = find_cg_rpool_locked(p, device); > > Here, too, you can look up the leaf node once and walk up the > hierarhcy. Maybe create a helper, say rdmacg_get_pool_and_lock(), > which looks up an existing node or creates all pools from leaf to root > and returns with the lock held? A explained above, I will reduce rpool_list_lock and dev_mutex to single rdmacg_mutex. Lookup will still continue to avoid storing extra parent, because lookup is for rpool which can be multiple per cgroup. > > ... >> +err: >> + spin_lock(&rpool_list_lock); >> + for (q = cg; q != p; q = parent_rdmacg(q)) >> + uncharge_cg_resource_locked(q, device, index); > > If some resources are not very plentiful and contended, dropping lock > before error handling like above could lead to spurious failures. It > looks like the above is from trying to create pool at each level while > charging up. Creating all necessary pools at the outset should make > the code simpler and more robust. Same comment as above. > >> + spin_unlock(&rpool_list_lock); >> + css_put(&cg->css); > > Ditto, where is this from? From task_get_css, called by get_current_rdmacg() during charging time. > >> +void rdmacg_query_limit(struct rdmacg_device *device, int *limits) >> +{ >> + struct rdma_cgroup *cg, *p; >> + struct rdmacg_resource_pool *rpool; >> + struct rdmacg_pool_info *pool_info; >> + int i; >> + >> + pool_info = &device->pool_info; >> + >> + for (i = 0; i < pool_info->table_len; i++) >> + limits[i] = S32_MAX; >> + >> + cg = get_current_rdmacg(); >> + /* >> + * Check in hirerchy which pool get the least amount of >> + * resource limits. >> + */ >> + spin_lock(&rpool_list_lock); >> + for (p = cg; p; p = parent_rdmacg(p)) { >> + rpool = find_cg_rpool_locked(cg, device); > > Ditto with lookup here. Same comment as above, need to have lookup. > >> +static struct rdmacg_device *rdmacg_get_device_locked(const char *name) >> +{ >> + struct rdmacg_device *device; > > lockdep_assert_held() would be nice. o.k. I will add this. > > + >> +static ssize_t rdmacg_resource_set_max(struct kernfs_open_file *of, >> + char *buf, size_t nbytes, loff_t off) >> +{ >> + struct rdma_cgroup *cg = css_rdmacg(of_css(of)); >> + const char *dev_name; >> + struct rdmacg_resource_pool *rpool; >> + struct rdmacg_device *device; >> + char *options = strstrip(buf); >> + struct rdmacg_pool_info *pool_info; >> + u64 enables = 0; >> + int *new_limits; >> + int i = 0, ret = 0; >> + >> + /* extract the device name first */ >> + dev_name = strsep(&options, " "); >> + if (!dev_name) { >> + ret = -EINVAL; >> + goto err; >> + } >> + >> + /* acquire lock to synchronize with hot plug devices */ >> + mutex_lock(&dev_mutex); >> + >> + device = rdmacg_get_device_locked(dev_name); >> + if (!device) { >> + ret = -ENODEV; >> + goto parse_err; >> + } >> + >> + pool_info = &device->pool_info; >> + >> + new_limits = kcalloc(pool_info->table_len, sizeof(int), GFP_KERNEL); >> + if (!new_limits) { >> + ret = -ENOMEM; >> + goto parse_err; >> + } > > Hmm... except for new_limits allocation and alloc_cg_rpool() > invocation, both of which can be done at the head of the function, > nothing seems to require a mutex here. If we move them to the head of > the function, can we get rid of dev_mutex entirely? No. As described in comment where lock is taken, it ensures that if device is being removed while configuration is going on, it protects against those race condition. So will keep it as it is. > >> + ret = rdmacg_parse_limits(options, pool_info, new_limits, &enables); >> + if (ret) >> + goto opt_err; >> + >> +retry: >> + spin_lock(&rpool_list_lock); >> + rpool = find_cg_rpool_locked(cg, device); >> + if (!rpool) { >> + spin_unlock(&rpool_list_lock); >> + ret = alloc_cg_rpool(cg, device); >> + if (ret) >> + goto opt_err; >> + else >> + goto retry; >> + } >> + >> + /* now set the new limits of the rpool */ >> + while (enables) { >> + /* if user set the limit, enables bit is set */ >> + if (enables & BIT(i)) { >> + enables &= ~BIT(i); >> + set_resource_limit(rpool, i, new_limits[i]); >> + } >> + i++; >> + } > > Maybe we can use for_each_set_bit()? ok. I will use that API. > >> + if (rpool->usage_sum == 0 && >> + rpool->num_max_cnt == pool_info->table_len) { >> + /* >> + * No user of the rpool and all entries are set to max, so >> + * safe to delete this rpool. >> + */ >> + list_del(&rpool->cg_list); >> + spin_unlock(&rpool_list_lock); >> + >> + free_cg_rpool(rpool); > > Can't we just count the number of resources which either have !max > setting or !0 usage? > What you have described here is done above. Instead of running loop to find that out for every resource, as you suggested last time, keeping two counters for usage and max to find out this condition. >> +static u32 *get_cg_rpool_values(struct rdma_cgroup *cg, >> + struct rdmacg_device *device, >> + enum rdmacg_file_type sf_type, >> + int count) >> +{ >> + struct rdmacg_resource_pool *rpool; >> + u32 *value_tbl; >> + int i, ret; >> + >> + value_tbl = kcalloc(count, sizeof(u32), GFP_KERNEL); >> + if (!value_tbl) { >> + ret = -ENOMEM; >> + goto err; >> + } > > Do we need this type of interface? Yes > Why not let the caller look up the > target pool and call this function with pool and resource index? I can move value_tbl allocation out of this function, but what is the problem in current code? I don't see any difference in moving loop count specific code outside of get_cg_rpool_values() function other than doing rework. What gain you are looking forward to by doing so? -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello, On Mon, Apr 04, 2016 at 03:50:54PM -0700, Parav Pandit wrote: > 2nd advantage is, it allows avoiding lot of rework, in bundling kernel > modules with different kernel versions. So it is certainly valuable > feature with almost nil complexity cost of code or memory that solves > two problems with approach. > If there two kernel versions with different type of resources and > kernel modules with different resources, it gets ugly to maintain that > kind of compatibility using compat.h. This approach avoid all such > cases. Is it actually customary to have rdma core module updated more frequently separate from the kernel? Out-of-tree modules being updated separately happens quite a bit but this is an in-kernel module, which usually is tightly coupled with the rest of the kernel. > > * It's usually a good idea to have hierarchical objects to be created > > all the way to the root when a leaf node is requested and link > > parent at each level. That way, when a descendant object is looked > > up, the caller can always deref its ->parent pointer till it reaches > > the top. > > This is interesting comment. I cannot recall, but I think its v4 or v5 > was exactly doing same. > Allocating resource pool first in one loop and charging them in another. > In event of failure, uncharging them in 3rd. > And you gave comment that time is to move away from that approach for > simplicity! > That I had refcnt on each object. I don't remember the details well but the code was vastly more complex back then and the object lifetime management was muddy at best. If I reviewed in a contradicting way, my apologies, but given the current code, it'd be better to have objects creation upfront. > > So, with each pool linking to its parent, instead of looking up at > > each level, it can just follow ->parent recursively. > > No. Lookup is being done for the rpool for that device and not the cgroup. > doing recursively using ->parent would require additional pointer of > rpool type to be maintained which is not necessary because we already > have cgroup level parent. Yes, I meant adding pool->parent field. Hierarchical operations become far simpler with the invariant that parent always exists. > Adding ->parent would make it little faster compare to traversing 1 to > 4 node entry list. However this is not hot path, so keeping existing > code to traverse is more desirable than adding ->parent of rpool type, > which also saves memory for large number of cgroup instances. It isn't necessarily about speed. It makes clear that the parent always should exist and makes the code easier to read and update. > >> + /* > >> + * A negative count (or overflow) is invalid, > >> + * it indicates a bug in the rdma controller. > >> + */ > >> + WARN_ON_ONCE(rpool->resources[index].usage < 0); > >> + rpool->usage_sum--; > > > > What guarantees that this count wouldn't overflow? More on this > > later. > > Are you suggesting to add WARN_ON for usage_sum variable for debugging? > I believe 1st warning is sufficient? I mean that it isn't particularly difficult to overflow a s32 when adding up multiple usages into one. > >> +static ssize_t rdmacg_resource_set_max(struct kernfs_open_file *of, > >> + char *buf, size_t nbytes, loff_t off) > >> +{ > >> + struct rdma_cgroup *cg = css_rdmacg(of_css(of)); > >> + const char *dev_name; > >> + struct rdmacg_resource_pool *rpool; > >> + struct rdmacg_device *device; > >> + char *options = strstrip(buf); > >> + struct rdmacg_pool_info *pool_info; > >> + u64 enables = 0; > >> + int *new_limits; > >> + int i = 0, ret = 0; > >> + > >> + /* extract the device name first */ > >> + dev_name = strsep(&options, " "); > >> + if (!dev_name) { > >> + ret = -EINVAL; > >> + goto err; > >> + } > >> + > >> + /* acquire lock to synchronize with hot plug devices */ > >> + mutex_lock(&dev_mutex); > >> + > >> + device = rdmacg_get_device_locked(dev_name); > >> + if (!device) { > >> + ret = -ENODEV; > >> + goto parse_err; > >> + } > >> + > >> + pool_info = &device->pool_info; > >> + > >> + new_limits = kcalloc(pool_info->table_len, sizeof(int), GFP_KERNEL); > >> + if (!new_limits) { > >> + ret = -ENOMEM; > >> + goto parse_err; > >> + } > > > > Hmm... except for new_limits allocation and alloc_cg_rpool() > > invocation, both of which can be done at the head of the function, > > nothing seems to require a mutex here. If we move them to the head of > > the function, can we get rid of dev_mutex entirely? > > No. As described in comment where lock is taken, > it ensures that if device is being removed while configuration is > going on, it protects against those race condition. > So will keep it as it is. Yeah, sure, it needs protection. I was wondering why it needed to be a separate mutex. The only sleeping operations seem to be the ones which can be done before or with acquiring rpool_list_lock, no? > >> + if (rpool->usage_sum == 0 && > >> + rpool->num_max_cnt == pool_info->table_len) { > >> + /* > >> + * No user of the rpool and all entries are set to max, so > >> + * safe to delete this rpool. > >> + */ > >> + list_del(&rpool->cg_list); > >> + spin_unlock(&rpool_list_lock); > >> + > >> + free_cg_rpool(rpool); > > > > Can't we just count the number of resources which either have !max > > setting or !0 usage? > > > What you have described here is done above. Instead of running loop to > find that out for every resource, You're summing up all usages instead of counting the number of !0 usages. > as you suggested last time, keeping two counters for usage and max to > find out this condition. So, whether the counters are separate or not doesn't matter that much but it's awkward that it's counting the number of !max entries for limits while summing the actual usages (instead of counting the number of !0 usages) especially given that it gets summed into an int counter. Wouldn't counting !max limit && !0 usage be more consistent? > >> +static u32 *get_cg_rpool_values(struct rdma_cgroup *cg, > >> + struct rdmacg_device *device, > >> + enum rdmacg_file_type sf_type, > >> + int count) > >> +{ > >> + struct rdmacg_resource_pool *rpool; > >> + u32 *value_tbl; > >> + int i, ret; > >> + > >> + value_tbl = kcalloc(count, sizeof(u32), GFP_KERNEL); > >> + if (!value_tbl) { > >> + ret = -ENOMEM; > >> + goto err; > >> + } > > > > Do we need this type of interface? > Yes > > Why not let the caller look up the > > target pool and call this function with pool and resource index? > > I can move value_tbl allocation out of this function, but what is the > problem in current code? > I don't see any difference in moving loop count specific code outside > of get_cg_rpool_values() function other than doing rework. What gain > you are looking forward to by doing so? I meant you don't need the allocation at all. lock; for_each_dev() { pool = lookup_pool(); for_each_field() seq_printf(sf, "%s ", name, pool_val(pool, index)); } unlock; I don't know why you end up missing basic patterns so badly. It's making the review and iteration process pretty painful. Please don't be confrontational and try to read the review comments assuming good will. Thanks.
Hi Tejun, On Mon, Apr 4, 2016 at 6:25 PM, Tejun Heo <tj@kernel.org> wrote: > Hello, > > On Mon, Apr 04, 2016 at 03:50:54PM -0700, Parav Pandit wrote: >> 2nd advantage is, it allows avoiding lot of rework, in bundling kernel >> modules with different kernel versions. So it is certainly valuable >> feature with almost nil complexity cost of code or memory that solves >> two problems with approach. >> If there two kernel versions with different type of resources and >> kernel modules with different resources, it gets ugly to maintain that >> kind of compatibility using compat.h. This approach avoid all such >> cases. > > Is it actually customary to have rdma core module updated more > frequently separate from the kernel? Out-of-tree modules being > updated separately happens quite a bit but this is an in-kernel > module, which usually is tightly coupled with the rest of the kernel. > Yes. rdma core module is compiled as kernel module. Its often updated for new features, fixes. So kernel version can be one but RDMA core module(s) get updated more frequently than kernel. > > I don't remember the details well but the code was vastly more complex > back then and the object lifetime management was muddy at best. If I > reviewed in a contradicting way, my apologies, but given the current > code, it'd be better to have objects creation upfront. Do you mean, try_charge() should lock() run loop to allocate in hierarchy, if not allocated. run loop again to charge. unlock() If so, I prefer to run the loop once. If you mean, objects creating upfront when cgroup is created, or when device is created - than we have talked of that approach in past, that its more complex than what is being done today. I would certainly want to avoid that in this patch as above approach has two advantages. (a) its simpler (b) doesn't require extra parent pointer, which is already available from cgroup > >> > So, with each pool linking to its parent, instead of looking up at >> > each level, it can just follow ->parent recursively. >> >> No. Lookup is being done for the rpool for that device and not the cgroup. >> doing recursively using ->parent would require additional pointer of >> rpool type to be maintained which is not necessary because we already >> have cgroup level parent. > > Yes, I meant adding pool->parent field. Hierarchical operations > become far simpler with the invariant that parent always exists. > >> Adding ->parent would make it little faster compare to traversing 1 to >> 4 node entry list. However this is not hot path, so keeping existing >> code to traverse is more desirable than adding ->parent of rpool type, >> which also saves memory for large number of cgroup instances. > > It isn't necessarily about speed. It makes clear that the parent > always should exist and makes the code easier to read and update. It doesn't have to exist. It can get allocated when charging occurs. Otherwise even if rdma resources are not used, it ends up allocating rpool in hierarchy. (We talked this before) > >> >> + /* >> >> + * A negative count (or overflow) is invalid, >> >> + * it indicates a bug in the rdma controller. >> >> + */ >> >> + WARN_ON_ONCE(rpool->resources[index].usage < 0); >> >> + rpool->usage_sum--; >> > >> > What guarantees that this count wouldn't overflow? More on this >> > later. >> >> Are you suggesting to add WARN_ON for usage_sum variable for debugging? >> I believe 1st warning is sufficient? > > I mean that it isn't particularly difficult to overflow a s32 when > adding up multiple usages into one. Possible,but resources are not really in range of 2G range, at least not any hardware that I am aware of. But I can make it u64. > >> >> +static ssize_t rdmacg_resource_set_max(struct kernfs_open_file *of, >> >> + char *buf, size_t nbytes, loff_t off) >> >> +{ >> >> + struct rdma_cgroup *cg = css_rdmacg(of_css(of)); >> >> + const char *dev_name; >> >> + struct rdmacg_resource_pool *rpool; >> >> + struct rdmacg_device *device; >> >> + char *options = strstrip(buf); >> >> + struct rdmacg_pool_info *pool_info; >> >> + u64 enables = 0; >> >> + int *new_limits; >> >> + int i = 0, ret = 0; >> >> + >> >> + /* extract the device name first */ >> >> + dev_name = strsep(&options, " "); >> >> + if (!dev_name) { >> >> + ret = -EINVAL; >> >> + goto err; >> >> + } >> >> + >> >> + /* acquire lock to synchronize with hot plug devices */ >> >> + mutex_lock(&dev_mutex); >> >> + >> >> + device = rdmacg_get_device_locked(dev_name); >> >> + if (!device) { >> >> + ret = -ENODEV; >> >> + goto parse_err; >> >> + } >> >> + >> >> + pool_info = &device->pool_info; >> >> + >> >> + new_limits = kcalloc(pool_info->table_len, sizeof(int), GFP_KERNEL); >> >> + if (!new_limits) { >> >> + ret = -ENOMEM; >> >> + goto parse_err; >> >> + } >> > >> > Hmm... except for new_limits allocation and alloc_cg_rpool() >> > invocation, both of which can be done at the head of the function, >> > nothing seems to require a mutex here. If we move them to the head of >> > the function, can we get rid of dev_mutex entirely? >> >> No. As described in comment where lock is taken, >> it ensures that if device is being removed while configuration is >> going on, it protects against those race condition. >> So will keep it as it is. > > Yeah, sure, it needs protection. I was wondering why it needed to be > a separate mutex. The only sleeping operations seem to be the ones > which can be done before or with acquiring rpool_list_lock, no? I will just make one mutex lock now. > >> >> + if (rpool->usage_sum == 0 && >> >> + rpool->num_max_cnt == pool_info->table_len) { >> >> + /* >> >> + * No user of the rpool and all entries are set to max, so >> >> + * safe to delete this rpool. >> >> + */ >> >> + list_del(&rpool->cg_list); >> >> + spin_unlock(&rpool_list_lock); >> >> + >> >> + free_cg_rpool(rpool); >> > >> > Can't we just count the number of resources which either have !max >> > setting or !0 usage? >> > >> What you have described here is done above. Instead of running loop to >> find that out for every resource, > > You're summing up all usages instead of counting the number of !0 > usages. I see now. Yeah, I will change that as well to make is consistent like !max_entries. > >> as you suggested last time, keeping two counters for usage and max to >> find out this condition. > > So, whether the counters are separate or not doesn't matter that much > but it's awkward that it's counting the number of !max entries for > limits while summing the actual usages (instead of counting the number > of !0 usages) especially given that it gets summed into an int > counter. Wouldn't counting !max limit && !0 usage be more consistent? > >> >> +static u32 *get_cg_rpool_values(struct rdma_cgroup *cg, >> >> + struct rdmacg_device *device, >> >> + enum rdmacg_file_type sf_type, >> >> + int count) >> >> +{ >> >> + struct rdmacg_resource_pool *rpool; >> >> + u32 *value_tbl; >> >> + int i, ret; >> >> + >> >> + value_tbl = kcalloc(count, sizeof(u32), GFP_KERNEL); >> >> + if (!value_tbl) { >> >> + ret = -ENOMEM; >> >> + goto err; >> >> + } >> > >> > Do we need this type of interface? >> Yes >> > Why not let the caller look up the >> > target pool and call this function with pool and resource index? >> >> I can move value_tbl allocation out of this function, but what is the >> problem in current code? >> I don't see any difference in moving loop count specific code outside >> of get_cg_rpool_values() function other than doing rework. What gain >> you are looking forward to by doing so? > > I meant you don't need the allocation at all. > > lock; > for_each_dev() { > pool = lookup_pool(); > for_each_field() > seq_printf(sf, "%s ", name, pool_val(pool, index)); > } > unlock; > > I don't know why you end up missing basic patterns so badly. It's > making the review and iteration process pretty painful. Please don't > be confrontational and try to read the review comments assuming good > will. > My understanding of seq_printf() being blocking call and accessing pool_info in spin lock context, made me allocate memory to get all values upfront through allocation. Now that the lock is going away, I can do what you have described above. > Thanks. > > -- > tejun -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Apr 04, 2016 at 09:25:04PM -0400, Tejun Heo wrote: > Is it actually customary to have rdma core module updated more > frequently separate from the kernel? Out-of-tree modules being > updated separately happens quite a bit but this is an in-kernel > module, which usually is tightly coupled with the rest of the kernel. People do it for all the wrong reasons - OFED and organization of morons wants people to use their modules, which causes lots of harm. Anything that makes this harder is a good thing. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Christoph, On Tue, Apr 5, 2016 at 2:06 AM, Christoph Hellwig <hch@infradead.org> wrote: > On Mon, Apr 04, 2016 at 09:25:04PM -0400, Tejun Heo wrote: >> Is it actually customary to have rdma core module updated more >> frequently separate from the kernel? Out-of-tree modules being >> updated separately happens quite a bit but this is an in-kernel >> module, which usually is tightly coupled with the rest of the kernel. > > People do it for all the wrong reasons - OFED and organization of morons > wants people to use their modules, which causes lots of harm. Anything > that makes this harder is a good thing. > I am not really trying to address OFED issues here. I am sure you understand that if ib_core.ko kernel module is in-kernel module than, for all the fixes/enhancements that goes to it would require people to upgrade to newer kernel, instead of just modules upgrade. Such heavy weight upgrade slows down the adoption which i am trying to avoid here by placing knobs in right kernel module's hand. Its like making ib_core.ko from module to in kernel component, if I understand correctly nobody wants to do that. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Apr 05, 2016 at 05:39:21AM -0700, Parav Pandit wrote: > I am not really trying to address OFED issues here. I am sure you > understand that if ib_core.ko kernel module is in-kernel module than, > for all the fixes/enhancements that goes to it would require people to > upgrade to newer kernel, instead of just modules upgrade. Such heavy > weight upgrade slows down the adoption which i am trying to avoid here > by placing knobs in right kernel module's hand. What a load of rubbish. The Linux kernel is one program and should be upgraded together. > Its like making ib_core.ko from module to in kernel component, if I > understand correctly nobody wants to do that. We allow splitting subsystems out where it's easily doable to avoid the resources consumption if they're all built in. For cgroups it's not really practical, but that doesn't mean you can upgrade invidual parts of a complex program without a lot of precaution. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Christoph, On Tue, Apr 5, 2016 at 5:42 AM, Christoph Hellwig <hch@infradead.org> wrote: > On Tue, Apr 05, 2016 at 05:39:21AM -0700, Parav Pandit wrote: >> I am not really trying to address OFED issues here. I am sure you >> understand that if ib_core.ko kernel module is in-kernel module than, >> for all the fixes/enhancements that goes to it would require people to >> upgrade to newer kernel, instead of just modules upgrade. Such heavy >> weight upgrade slows down the adoption which i am trying to avoid here >> by placing knobs in right kernel module's hand. > > What a load of rubbish. The Linux kernel is one program and should be > upgraded together. Just because we add one more rdma resource, we need to ask someone to upgrade kernel? Flexibility is coming at very minimal cost, so what exactly is the issue in having that instead of forcing architecture to give away that? Whole code is hardly 700 odd lines. > >> Its like making ib_core.ko from module to in kernel component, if I >> understand correctly nobody wants to do that. > > We allow splitting subsystems out where it's easily doable to avoid the > resources consumption if they're all built in. For cgroups it's not > really practical, but that doesn't mean you can upgrade invidual parts > of a complex program without a lot of precaution. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello, Parav. On Mon, Apr 04, 2016 at 07:22:38PM -0700, Parav Pandit wrote: > > Is it actually customary to have rdma core module updated more > > frequently separate from the kernel? Out-of-tree modules being > > updated separately happens quite a bit but this is an in-kernel > > module, which usually is tightly coupled with the rest of the kernel. > > > Yes. > rdma core module is compiled as kernel module. > Its often updated for new features, fixes. > So kernel version can be one but RDMA core module(s) get updated more > frequently than kernel. As it is a fairly isolated domain, to certain extent, it could be okay to let it go. At the same time, I know that these enterprise things tend to go completely wayward and am worried about individual drivers going crazy with custom attributes in a non-sensical way. The interface this patch is proposing easily allows that and that at the cost of internal engineering flexibility. I don't really want to be caught up in a situation where we're forced to include broken usages because that's what's already out in the wild. I personally would much prefer the resources to be defined rigidly. Let's see how the discussion with Christoph evolves. > > I don't remember the details well but the code was vastly more complex > > back then and the object lifetime management was muddy at best. If I > > reviewed in a contradicting way, my apologies, but given the current > > code, it'd be better to have objects creation upfront. > > Do you mean, > try_charge() should > lock() > run loop to allocate in hierarchy, if not allocated. > run loop again to charge. > unlock() > > If so, I prefer to run the loop once. In the original review message, I mentioned creating an interface which creates the hierarchy of objects as necessary and returns the target pool with lock held, can you please give it a shot? Something like the following. pool *get_pool(...) { lock; if (target pool exists) return pool w/ lock held; create the pool hierarchically (might involve unlock); if (succeeded) return pool w/ lock held; return NULL w/o lock; } > > It isn't necessarily about speed. It makes clear that the parent > > always should exist and makes the code easier to read and update. > > It doesn't have to exist. It can get allocated when charging occurs. > Otherwise even if rdma resources are not used, it ends up allocating > rpool in hierarchy. (We talked this before) Sure, create pools only for the used combinations but do that hierarchically so that a child pool always has a parent. I can promise you that the code will read a lot better with that. > > I don't know why you end up missing basic patterns so badly. It's > > making the review and iteration process pretty painful. Please don't > > be confrontational and try to read the review comments assuming good > > will. > > > My understanding of seq_printf() being blocking call and accessing seq_printf() can be called from any context; otherwise, it would be a horrible interface to use, wouldn't it? > pool_info in spin lock context, made me allocate memory to get all > values upfront through allocation. > Now that the lock is going away, I can do what you have described above. Thanks.
Just one more thing. On Tue, Apr 05, 2016 at 10:01:07AM -0400, Tejun Heo wrote: ... > > pool_info in spin lock context, made me allocate memory to get all > > values upfront through allocation. > > Now that the lock is going away, I can do what you have described above. So, this might be okay depending on the use case but it often becomes painful to require sleeping context for freeing resources. If you're certain that requiring sleeping context is okay for all paths, using a single mutex is fine but *usually* it isn't a great idea. Thanks.
On Tue, Apr 5, 2016 at 7:07 AM, Tejun Heo <tj@kernel.org> wrote: > Just one more thing. > > On Tue, Apr 05, 2016 at 10:01:07AM -0400, Tejun Heo wrote: > ... >> > pool_info in spin lock context, made me allocate memory to get all >> > values upfront through allocation. >> > Now that the lock is going away, I can do what you have described above. > > So, this might be okay depending on the use case but it often becomes > painful to require sleeping context for freeing resources. If you're > certain that requiring sleeping context is okay for all paths, using a > single mutex is fine but *usually* it isn't a great idea. > At present charge and uncharge are from sleeping context. > > -- > tejun -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Apr 5, 2016 at 7:01 AM, Tejun Heo <tj@kernel.org> wrote: > Hello, Parav. > > On Mon, Apr 04, 2016 at 07:22:38PM -0700, Parav Pandit wrote: >> > Is it actually customary to have rdma core module updated more >> > frequently separate from the kernel? Out-of-tree modules being >> > updated separately happens quite a bit but this is an in-kernel >> > module, which usually is tightly coupled with the rest of the kernel. >> > >> Yes. >> rdma core module is compiled as kernel module. >> Its often updated for new features, fixes. >> So kernel version can be one but RDMA core module(s) get updated more >> frequently than kernel. > > As it is a fairly isolated domain, to certain extent, it could be okay > to let it go. At the same time, I know that these enterprise things > tend to go completely wayward and am worried about individual drivers > going crazy with custom attributes in a non-sensical way. If its crazy at driver level, I am sure it will be equally crazy for any end-user too. Therefore no user would use those crazy resources either. Intent is certainly not for the individual drivers as we agreed in past. IB stack maintainers would be reviewing new enum addition anyway, whether its verb or hw resource (unlikely). > The > interface this patch is proposing easily allows that and that at the > cost of internal engineering flexibility. I don't really want to be > caught up in a situation where we're forced to include broken usages > because that's what's already out in the wild. I personally would > much prefer the resources to be defined rigidly. Let's see how the > discussion with Christoph evolves. > Sure. I will wait for his comments. >> > I don't remember the details well but the code was vastly more complex >> > back then and the object lifetime management was muddy at best. If I >> > reviewed in a contradicting way, my apologies, but given the current >> > code, it'd be better to have objects creation upfront. >> >> Do you mean, >> try_charge() should >> lock() >> run loop to allocate in hierarchy, if not allocated. >> run loop again to charge. >> unlock() >> >> If so, I prefer to run the loop once. > > In the original review message, I mentioned creating an interface > which creates the hierarchy of objects as necessary and returns the > target pool with lock held, can you please give it a shot? Something > like the following. o.k. I will attempt. Looks doable. I am on travel so it will take few more days for me to turn around with below approach with tested code. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello, Parav. On Tue, Apr 05, 2016 at 07:25:11AM -0700, Parav Pandit wrote: > > As it is a fairly isolated domain, to certain extent, it could be okay > > to let it go. At the same time, I know that these enterprise things > > tend to go completely wayward and am worried about individual drivers > > going crazy with custom attributes in a non-sensical way. > > If its crazy at driver level, I am sure it will be equally crazy for > any end-user too. Therefore no user would use those crazy resources > either. So, the above paragraph simply isn't true. It's not difficult to twist things bit so that things work in a hackish and often horrible way and we know this happens quite a bit, especially in enterprise settings. > Intent is certainly not for the individual drivers as we agreed in > past. You and I agreeing to that doesn't really matter all that much. > IB stack maintainers would be reviewing new enum addition > anyway, whether its verb or hw resource (unlikely). Well, if the additions are unlikely... > > In the original review message, I mentioned creating an interface > > which creates the hierarchy of objects as necessary and returns the > > target pool with lock held, can you please give it a shot? Something > > like the following. > > o.k. I will attempt. Looks doable. > I am on travel so it will take few more days for me to turn around > with below approach with tested code. So, if you go with single mutex, you don't really need get_and_lock semantics, you can just call the get function with mutex held. Please do whichever looks best. Thanks.
On Tue, Apr 05, 2016 at 05:55:26AM -0700, Parav Pandit wrote: > Hi Christoph, > > On Tue, Apr 5, 2016 at 5:42 AM, Christoph Hellwig <hch@infradead.org> wrote: > > On Tue, Apr 05, 2016 at 05:39:21AM -0700, Parav Pandit wrote: > >> I am not really trying to address OFED issues here. I am sure you > >> understand that if ib_core.ko kernel module is in-kernel module than, > >> for all the fixes/enhancements that goes to it would require people to > >> upgrade to newer kernel, instead of just modules upgrade. Such heavy > >> weight upgrade slows down the adoption which i am trying to avoid here > >> by placing knobs in right kernel module's hand. > > > > What a load of rubbish. The Linux kernel is one program and should be > > upgraded together. > > Just because we add one more rdma resource, we need to ask someone to > upgrade kernel? It doesn't make sense. Kernel and modules are always coming together, the attempts to mix kernel and modules from different versions can lead to many interesting debug scenarios. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Apr 05, 2016 at 05:55:26AM -0700, Parav Pandit wrote: > Just because we add one more rdma resource, we need to ask someone to > upgrade kernel? Yes. Just like when you need any other core kernel resource. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Christoph, I was on travel. Sorry for the late inline response and question. Parav On Tue, Apr 5, 2016 at 10:57 PM, Christoph Hellwig <hch@infradead.org> wrote: > On Tue, Apr 05, 2016 at 05:55:26AM -0700, Parav Pandit wrote: >> Just because we add one more rdma resource, we need to ask someone to >> upgrade kernel? > > Yes. Just like when you need any other core kernel resource. By architecture Linux kernel allows (a) plugin of any new block level IO scheduler as kernel module. This is much more fundamental resource or functionality than rdma resource. (b) plugin of any new file system as kernel module. Changing both in field and out of box can do be more harmful than defining new rdma resource. RDMA Resource definition by IB core module is very similar to above two functionality, where elevator and VFS provides basic support framework and so rdma cgroup controller here. So can you please help me understand - which resource did you compare against in your above comment for "core kernel resource"? I compared it with similar functionality, flexibility given by (a) block IO Scheduler and (b) VFS subsystem to implement them as kernel module. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/cgroup_rdma.h b/include/linux/cgroup_rdma.h new file mode 100644 index 0000000..baec8f0 --- /dev/null +++ b/include/linux/cgroup_rdma.h @@ -0,0 +1,52 @@ +#ifndef _CGROUP_RDMA_H +#define _CGROUP_RDMA_H + +#include <linux/cgroup.h> + +#ifdef CONFIG_CGROUP_RDMA + +struct rdma_cgroup { + struct cgroup_subsys_state css; + + /* protects resource pool list */ + spinlock_t rpool_list_lock; + /* + * head to keep track of all resource pools + * that belongs to this cgroup. + */ + struct list_head rpool_head; +}; + +struct rdmacg_pool_info { + const char **resource_name_table; + int table_len; +}; + +struct rdmacg_device { + struct rdmacg_pool_info pool_info; + struct list_head rdmacg_list; + struct list_head rpool_head; + /* protects resource pool list */ + spinlock_t rpool_lock; + char *name; +}; + +/* + * APIs for RDMA/IB stack to publish when a device wants to + * participate in resource accounting + */ +int rdmacg_register_device(struct rdmacg_device *device); +void rdmacg_unregister_device(struct rdmacg_device *device); + +/* APIs for RDMA/IB stack to charge/uncharge pool specific resources */ +int rdmacg_try_charge(struct rdma_cgroup **rdmacg, + struct rdmacg_device *device, + int resource_index); +void rdmacg_uncharge(struct rdma_cgroup *cg, + struct rdmacg_device *device, + int resource_index); +void rdmacg_query_limit(struct rdmacg_device *device, + int *limits); + +#endif /* CONFIG_CGROUP_RDMA */ +#endif /* _CGROUP_RDMA_H */ diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h index 0df0336a..d0e597c 100644 --- a/include/linux/cgroup_subsys.h +++ b/include/linux/cgroup_subsys.h @@ -56,6 +56,10 @@ SUBSYS(hugetlb) SUBSYS(pids) #endif +#if IS_ENABLED(CONFIG_CGROUP_RDMA) +SUBSYS(rdma) +#endif + /* * The following subsystems are not supported on the default hierarchy. */ diff --git a/init/Kconfig b/init/Kconfig index 2232080..0d3efe0 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1054,6 +1054,16 @@ config CGROUP_PIDS since the PIDs limit only affects a process's ability to fork, not to attach to a cgroup. +config CGROUP_RDMA + bool "RDMA controller" + help + Provides enforcement of RDMA resources defined by IB stack. + It is fairly easy for consumers to exhaust RDMA resources, which + can result into resource unavailability to other consumers. + RDMA controller is designed to stop this from happening. + Attaching processes with active RDMA resources to the cgroup + hierarchy is allowed even if can cross the hierarchy's limit. + config CGROUP_FREEZER bool "Freezer controller" help diff --git a/kernel/Makefile b/kernel/Makefile index 53abf00..26e413c 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -57,6 +57,7 @@ obj-$(CONFIG_COMPAT) += compat.o obj-$(CONFIG_CGROUPS) += cgroup.o obj-$(CONFIG_CGROUP_FREEZER) += cgroup_freezer.o obj-$(CONFIG_CGROUP_PIDS) += cgroup_pids.o +obj-$(CONFIG_CGROUP_RDMA) += cgroup_rdma.o obj-$(CONFIG_CPUSETS) += cpuset.o obj-$(CONFIG_UTS_NS) += utsname.o obj-$(CONFIG_USER_NS) += user_namespace.o diff --git a/kernel/cgroup_rdma.c b/kernel/cgroup_rdma.c new file mode 100644 index 0000000..21dd27a --- /dev/null +++ b/kernel/cgroup_rdma.c @@ -0,0 +1,746 @@ +/* + * This file is subject to the terms and conditions of version 2 of the GNU + * General Public License. See the file COPYING in the main directory of the + * Linux distribution for more details. + */ + +#include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/seq_file.h> +#include <linux/cgroup.h> +#include <linux/parser.h> +#include <linux/cgroup_rdma.h> + +#define RDMACG_MAX_STR "max" + +static DEFINE_MUTEX(dev_mutex); +static LIST_HEAD(dev_list_head); + +/* + * Protects list of resource pools maintained on per cgroup basis. + */ +static spinlock_t rpool_list_lock = __SPIN_LOCK_UNLOCKED(&rpool_list_lock); + +enum rdmacg_file_type { + RDMACG_RESOURCE_MAX, + RDMACG_RESOURCE_STAT, +}; + +/* resource tracker for each resource for rdma cgroup */ +struct rdmacg_resource { + int max; + int usage; +}; + +/* + * resource pool object which represents per cgroup, per device + * resources. There are multiple instance of this object per cgroup, + * therefore it cannot be embedded within rdma_cgroup structure. It + * is maintained as list. + */ +struct rdmacg_resource_pool { + struct list_head cg_list; + struct list_head dev_list; + + struct rdmacg_device *device; + struct rdmacg_resource *resources; + + /* count active user tasks of this pool */ + int usage_sum; + /* total number counts which are set to max */ + int num_max_cnt; +}; + +static struct rdma_cgroup *css_rdmacg(struct cgroup_subsys_state *css) +{ + return container_of(css, struct rdma_cgroup, css); +} + +static struct rdma_cgroup *parent_rdmacg(struct rdma_cgroup *cg) +{ + return css_rdmacg(cg->css.parent); +} + +static inline struct rdma_cgroup *get_current_rdmacg(void) +{ + return css_rdmacg(task_get_css(current, rdma_cgrp_id)); +} + +static void set_resource_limit(struct rdmacg_resource_pool *rpool, + int index, int new_max) +{ + if (new_max == S32_MAX) { + if (rpool->resources[index].max != S32_MAX) + rpool->num_max_cnt++; + } else { + if (rpool->resources[index].max == S32_MAX) + rpool->num_max_cnt--; + } + rpool->resources[index].max = new_max; +} + +static void set_all_resource_max_limit(struct rdmacg_resource_pool *rpool) +{ + struct rdmacg_pool_info *pool_info = &rpool->device->pool_info; + int i; + + for (i = 0; i < pool_info->table_len; i++) + set_resource_limit(rpool, i, S32_MAX); +} + +static void free_cg_rpool_mem(struct rdmacg_resource_pool *rpool) +{ + kfree(rpool->resources); + kfree(rpool); +} + +static void free_cg_rpool(struct rdmacg_resource_pool *rpool) +{ + spin_lock(&rpool->device->rpool_lock); + list_del(&rpool->dev_list); + spin_unlock(&rpool->device->rpool_lock); + + free_cg_rpool_mem(rpool); +} + +static struct rdmacg_resource_pool * +find_cg_rpool_locked(struct rdma_cgroup *cg, + struct rdmacg_device *device) + +{ + struct rdmacg_resource_pool *pool; + + lockdep_assert_held(&rpool_list_lock); + + list_for_each_entry(pool, &cg->rpool_head, cg_list) + if (pool->device == device) + return pool; + + return NULL; +} + +static int +alloc_cg_rpool(struct rdma_cgroup *cg, struct rdmacg_device *device) +{ + struct rdmacg_resource_pool *rpool, *other_rpool; + struct rdmacg_pool_info *pool_info = &device->pool_info; + int ret; + + rpool = kzalloc(sizeof(*rpool), GFP_KERNEL); + if (!rpool) { + ret = -ENOMEM; + goto err; + } + rpool->resources = kcalloc(pool_info->table_len, + sizeof(*rpool->resources), + GFP_KERNEL); + if (!rpool->resources) { + ret = -ENOMEM; + goto alloc_err; + } + + rpool->device = device; + INIT_LIST_HEAD(&rpool->cg_list); + INIT_LIST_HEAD(&rpool->dev_list); + spin_lock_init(&device->rpool_lock); + set_all_resource_max_limit(rpool); + + spin_lock(&rpool_list_lock); + + other_rpool = find_cg_rpool_locked(cg, device); + + /* + * if other task added resource pool for this device for this cgroup + * than free up which was recently created and use the one we found. + */ + if (other_rpool) { + spin_unlock(&rpool_list_lock); + free_cg_rpool(rpool); + return 0; + } + + list_add_tail(&rpool->cg_list, &cg->rpool_head); + + spin_lock(&device->rpool_lock); + list_add_tail(&rpool->dev_list, &device->rpool_head); + spin_unlock(&device->rpool_lock); + + spin_unlock(&rpool_list_lock); + return 0; + +alloc_err: + kfree(rpool); +err: + return ret; +} + +/** + * uncharge_cg_resource_locked - uncharge resource for rdma cgroup + * @cg: pointer to cg to uncharge and all parents in hierarchy + * @device: pointer to ib device + * @index: index of the resource to uncharge in cg (resource pool) + * + * It also frees the resource pool which was created as part of + * charging operation when there are no resources attached to + * resource pool. + */ +static void +uncharge_cg_resource_locked(struct rdma_cgroup *cg, + struct rdmacg_device *device, + int index) +{ + struct rdmacg_resource_pool *rpool; + struct rdmacg_pool_info *pool_info = &device->pool_info; + + rpool = find_cg_rpool_locked(cg, device); + + /* + * rpool cannot be null at this stage. Let kernel operate in case + * if there a bug in IB stack or rdma controller, instead of crashing + * the system. + */ + if (unlikely(!rpool)) { + pr_warn("Invalid device %p or rdma cgroup %p\n", cg, device); + return; + } + + rpool->resources[index].usage--; + + /* + * A negative count (or overflow) is invalid, + * it indicates a bug in the rdma controller. + */ + WARN_ON_ONCE(rpool->resources[index].usage < 0); + rpool->usage_sum--; + if (rpool->usage_sum == 0 && + rpool->num_max_cnt == pool_info->table_len) { + /* + * No user of the rpool and all entries are set to max, so + * safe to delete this rpool. + */ + list_del(&rpool->cg_list); + free_cg_rpool(rpool); + } +} + +/** + * rdmacg_uncharge_resource - hierarchically uncharge rdma resource count + * @device: pointer to rdmacg device + * @index: index of the resource to uncharge in cg in given resource pool + * @num: the number of rdma resource to uncharge + * + */ +void rdmacg_uncharge(struct rdma_cgroup *cg, + struct rdmacg_device *device, + int index) +{ + struct rdma_cgroup *p; + + spin_lock(&rpool_list_lock); + for (p = cg; p; p = parent_rdmacg(p)) + uncharge_cg_resource_locked(p, device, index); + spin_unlock(&rpool_list_lock); + + css_put(&cg->css); +} +EXPORT_SYMBOL(rdmacg_uncharge); + +/** + * rdmacg_try_charge_resource - hierarchically try to charge the rdma resource + * @rdmacg: pointer to rdma cgroup which will own this resource + * @device: pointer to rdmacg device + * @index: index of the resource to charge in cg (resource pool) + * + * This function follows charging resource in hierarchical way. + * It will fail if the charge would cause the new value to exceed the + * hierarchical limit. + * Returns 0 if the charge succeded, otherwise -EAGAIN, -ENOMEM or -EINVAL. + * Returns pointer to rdmacg for this resource when charging is successful. + * + * Charger needs to account resources on two criteria. + * (a) per cgroup & (b) per device resource usage. + * Per cgroup resource usage ensures that tasks of cgroup doesn't cross + * the configured limits. Per device provides granular configuration + * in multi device usage. It allocates resource pool in the hierarchy + * for each parent it come across for first resource. Later on resource + * pool will be available. Therefore it will be much faster thereon + * to charge/uncharge. + */ +int rdmacg_try_charge(struct rdma_cgroup **rdmacg, + struct rdmacg_device *device, + int index) +{ + struct rdma_cgroup *cg, *p, *q; + struct rdmacg_resource_pool *rpool; + s64 new; + int ret = 0; + + /* + * hold on to css, as cgroup can be removed but resource + * accounting happens on css. + */ + cg = get_current_rdmacg(); + + spin_lock(&rpool_list_lock); + for (p = cg; p; p = parent_rdmacg(p)) { +retry: + rpool = find_cg_rpool_locked(p, device); + if (rpool) { + new = rpool->resources[index].usage + 1; + if (new > rpool->resources[index].max) { + spin_unlock(&rpool_list_lock); + ret = -EAGAIN; + goto err; + } else { + rpool->resources[index].usage = new; + rpool->usage_sum++; + } + } else { + spin_unlock(&rpool_list_lock); + ret = alloc_cg_rpool(p, device); + if (ret) { + goto err; + } else { + spin_lock(&rpool_list_lock); + goto retry; + } + } + } + spin_unlock(&rpool_list_lock); + + *rdmacg = cg; + return 0; + +err: + spin_lock(&rpool_list_lock); + for (q = cg; q != p; q = parent_rdmacg(q)) + uncharge_cg_resource_locked(q, device, index); + spin_unlock(&rpool_list_lock); + css_put(&cg->css); + return ret; +} +EXPORT_SYMBOL(rdmacg_try_charge); + +/** + * rdmacg_register_rdmacg_device - register rdmacg device to rdma controller. + * @device: pointer to rdmacg device whose resources need to be accounted. + * + * If IB stack wish a device to participate in rdma cgroup resource + * tracking, it must invoke this API to register with rdma cgroup before + * any user space application can start using the RDMA resources. + * Returns 0 on success or EINVAL when table length given is beyond + * supported size. + */ +int rdmacg_register_device(struct rdmacg_device *device) +{ + if (device->pool_info.table_len > 64) + return -EINVAL; + + INIT_LIST_HEAD(&device->rdmacg_list); + INIT_LIST_HEAD(&device->rpool_head); + spin_lock_init(&device->rpool_lock); + + mutex_lock(&dev_mutex); + list_add_tail(&device->rdmacg_list, &dev_list_head); + mutex_unlock(&dev_mutex); + return 0; +} +EXPORT_SYMBOL(rdmacg_register_device); + +/** + * rdmacg_unregister_rdmacg_device - unregister the rdmacg device + * from rdma controller. + * @device: pointer to rdmacg device which was previously registered with rdma + * controller using rdmacg_register_device(). + * + * IB stack must invoke this after all the resources of the IB device + * are destroyed and after ensuring that no more resources will be created + * when this API is invoked. + */ +void rdmacg_unregister_device(struct rdmacg_device *device) +{ + struct rdmacg_resource_pool *rpool, *tmp; + + /* + * Synchronize with any active resource settings, + * usage query happening via configfs. + * At this stage, there should not be any active resource pools + * for this device, as RDMA/IB stack is expected to shutdown, + * tear down all the applications and free up resources. + */ + mutex_lock(&dev_mutex); + list_del_init(&device->rdmacg_list); + mutex_unlock(&dev_mutex); + + /* + * Now that this device off the cgroup list, its safe to free + * all the rpool resources. + */ + list_for_each_entry_safe(rpool, tmp, &device->rpool_head, dev_list) { + list_del_init(&rpool->dev_list); + + spin_lock(&rpool_list_lock); + list_del_init(&rpool->cg_list); + spin_unlock(&rpool_list_lock); + + free_cg_rpool_mem(rpool); + } +} +EXPORT_SYMBOL(rdmacg_unregister_device); + +/** + * rdmacg_query_limit - query the resource limits that + * might have been configured by the user. + * @device: pointer to ib device + * @type: the type of resource pool to know the limits of. + * @limits: pointer to an array of limits where rdma cg will provide + * the configured limits of the cgroup. + * + * This function honors resource limit in hierarchical way. + * In a cgroup hirarchy, it considers the limit of a controller which has + * smallest limit configured. + */ +void rdmacg_query_limit(struct rdmacg_device *device, int *limits) +{ + struct rdma_cgroup *cg, *p; + struct rdmacg_resource_pool *rpool; + struct rdmacg_pool_info *pool_info; + int i; + + pool_info = &device->pool_info; + + for (i = 0; i < pool_info->table_len; i++) + limits[i] = S32_MAX; + + cg = get_current_rdmacg(); + /* + * Check in hirerchy which pool get the least amount of + * resource limits. + */ + spin_lock(&rpool_list_lock); + for (p = cg; p; p = parent_rdmacg(p)) { + rpool = find_cg_rpool_locked(cg, device); + if (!rpool) + continue; + + for (i = 0; i < pool_info->table_len; i++) + limits[i] = min_t(int, limits[i], + rpool->resources[i].max); + } + spin_unlock(&rpool_list_lock); + css_put(&cg->css); +} +EXPORT_SYMBOL(rdmacg_query_limit); + +static int parse_resource(char *c, struct rdmacg_pool_info *pool_info, + int *intval) +{ + substring_t argstr; + const char **table = pool_info->resource_name_table; + char *name, *value = c; + size_t len; + int ret, i = 0; + + name = strsep(&value, "="); + if (!name || !value) + return -EINVAL; + + len = strlen(value); + + for (i = 0; i < pool_info->table_len; i++) { + if (strcmp(table[i], name)) + continue; + + argstr.from = value; + argstr.to = value + len; + + ret = match_int(&argstr, intval); + if (ret >= 0) { + if (*intval < 0) + break; + return i; + } + if (strncmp(value, RDMACG_MAX_STR, len) == 0) { + *intval = S32_MAX; + return i; + } + break; + } + return -EINVAL; +} + +static int rdmacg_parse_limits(char *options, + struct rdmacg_pool_info *pool_info, + int *new_limits, u64 *enables) +{ + char *c; + int err = -EINVAL; + + /* parse resource options */ + while ((c = strsep(&options, " ")) != NULL) { + int index, intval; + + index = parse_resource(c, pool_info, &intval); + if (index < 0) + goto err; + + new_limits[index] = intval; + *enables |= BIT(index); + } + return 0; + +err: + return err; +} + +static struct rdmacg_device *rdmacg_get_device_locked(const char *name) +{ + struct rdmacg_device *device; + + list_for_each_entry(device, &dev_list_head, rdmacg_list) + if (!strcmp(name, device->name)) + return device; + + return NULL; +} + +static ssize_t rdmacg_resource_set_max(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off) +{ + struct rdma_cgroup *cg = css_rdmacg(of_css(of)); + const char *dev_name; + struct rdmacg_resource_pool *rpool; + struct rdmacg_device *device; + char *options = strstrip(buf); + struct rdmacg_pool_info *pool_info; + u64 enables = 0; + int *new_limits; + int i = 0, ret = 0; + + /* extract the device name first */ + dev_name = strsep(&options, " "); + if (!dev_name) { + ret = -EINVAL; + goto err; + } + + /* acquire lock to synchronize with hot plug devices */ + mutex_lock(&dev_mutex); + + device = rdmacg_get_device_locked(dev_name); + if (!device) { + ret = -ENODEV; + goto parse_err; + } + + pool_info = &device->pool_info; + + new_limits = kcalloc(pool_info->table_len, sizeof(int), GFP_KERNEL); + if (!new_limits) { + ret = -ENOMEM; + goto parse_err; + } + + ret = rdmacg_parse_limits(options, pool_info, new_limits, &enables); + if (ret) + goto opt_err; + +retry: + spin_lock(&rpool_list_lock); + rpool = find_cg_rpool_locked(cg, device); + if (!rpool) { + spin_unlock(&rpool_list_lock); + ret = alloc_cg_rpool(cg, device); + if (ret) + goto opt_err; + else + goto retry; + } + + /* now set the new limits of the rpool */ + while (enables) { + /* if user set the limit, enables bit is set */ + if (enables & BIT(i)) { + enables &= ~BIT(i); + set_resource_limit(rpool, i, new_limits[i]); + } + i++; + } + + if (rpool->usage_sum == 0 && + rpool->num_max_cnt == pool_info->table_len) { + /* + * No user of the rpool and all entries are set to max, so + * safe to delete this rpool. + */ + list_del(&rpool->cg_list); + spin_unlock(&rpool_list_lock); + + free_cg_rpool(rpool); + } else { + spin_unlock(&rpool_list_lock); + } + +opt_err: + kfree(new_limits); +parse_err: + mutex_unlock(&dev_mutex); +err: + return ret ?: nbytes; +} + +static u32 *get_cg_rpool_values(struct rdma_cgroup *cg, + struct rdmacg_device *device, + enum rdmacg_file_type sf_type, + int count) +{ + struct rdmacg_resource_pool *rpool; + u32 *value_tbl; + int i, ret; + + value_tbl = kcalloc(count, sizeof(u32), GFP_KERNEL); + if (!value_tbl) { + ret = -ENOMEM; + goto err; + } + + spin_lock(&rpool_list_lock); + + rpool = find_cg_rpool_locked(cg, device); + + for (i = 0; i < count; i++) { + if (sf_type == RDMACG_RESOURCE_MAX) { + if (rpool) + value_tbl[i] = rpool->resources[i].max; + else + value_tbl[i] = S32_MAX; + } else { + if (rpool) + value_tbl[i] = rpool->resources[i].usage; + } + } + + spin_unlock(&rpool_list_lock); + + return value_tbl; + +err: + return ERR_PTR(ret); +} + +static void print_rpool_values(struct seq_file *sf, + struct rdmacg_pool_info *pool_info, + u32 *value_tbl) +{ + int i; + + for (i = 0; i < pool_info->table_len; i++) { + seq_puts(sf, pool_info->resource_name_table[i]); + seq_putc(sf, '='); + if (value_tbl[i] == S32_MAX) + seq_puts(sf, RDMACG_MAX_STR); + else + seq_printf(sf, "%d", value_tbl[i]); + seq_putc(sf, ' '); + } +} + +static int rdmacg_resource_read(struct seq_file *sf, void *v) +{ + struct rdmacg_device *device; + struct rdma_cgroup *cg = css_rdmacg(seq_css(sf)); + struct rdmacg_pool_info *pool_info; + u32 *value_tbl; + int ret = 0; + + mutex_lock(&dev_mutex); + + list_for_each_entry(device, &dev_list_head, rdmacg_list) { + pool_info = &device->pool_info; + + /* get the value from resource pool */ + value_tbl = get_cg_rpool_values(cg, device, + seq_cft(sf)->private, + pool_info->table_len); + if (IS_ERR_OR_NULL(value_tbl)) { + ret = -ENOMEM; + break; + } + + seq_printf(sf, "%s ", device->name); + print_rpool_values(sf, pool_info, value_tbl); + seq_putc(sf, '\n'); + kfree(value_tbl); + } + + mutex_unlock(&dev_mutex); + return ret; +} + +static struct cftype rdmacg_files[] = { + { + .name = "max", + .write = rdmacg_resource_set_max, + .seq_show = rdmacg_resource_read, + .private = RDMACG_RESOURCE_MAX, + .flags = CFTYPE_NOT_ON_ROOT, + }, + { + .name = "current", + .seq_show = rdmacg_resource_read, + .private = RDMACG_RESOURCE_STAT, + .flags = CFTYPE_NOT_ON_ROOT, + }, + { } /* terminate */ +}; + +static struct cgroup_subsys_state * +rdmacg_css_alloc(struct cgroup_subsys_state *parent) +{ + struct rdma_cgroup *cg; + + cg = kzalloc(sizeof(*cg), GFP_KERNEL); + if (!cg) + return ERR_PTR(-ENOMEM); + + INIT_LIST_HEAD(&cg->rpool_head); + spin_lock_init(&rpool_list_lock); + return &cg->css; +} + +static void rdmacg_css_free(struct cgroup_subsys_state *css) +{ + struct rdma_cgroup *cg = css_rdmacg(css); + + kfree(cg); +} + +/** + * rdmacg_css_offline - cgroup css_offline callback + * @css: css of interest + * + * This function is called when @css is about to go away and responsible + * for shooting down all rdmacg associated with @css. As part of that it + * marks all the resource pool entries to max value, so that when resources are + * uncharged, associated resource pool can be freed as well. + */ +static void rdmacg_css_offline(struct cgroup_subsys_state *css) +{ + struct rdma_cgroup *cg = css_rdmacg(css); + struct rdmacg_resource_pool *rpool; + + spin_lock(&rpool_list_lock); + + list_for_each_entry(rpool, &cg->rpool_head, cg_list) + set_all_resource_max_limit(rpool); + + spin_unlock(&rpool_list_lock); +} + +struct cgroup_subsys rdma_cgrp_subsys = { + .css_alloc = rdmacg_css_alloc, + .css_free = rdmacg_css_free, + .css_offline = rdmacg_css_offline, + .legacy_cftypes = rdmacg_files, + .dfl_cftypes = rdmacg_files, +};
Added rdma cgroup controller that does accounting, limit enforcement on rdma/IB verbs and hw resources. Added rdma cgroup header file which defines its APIs to perform charing/uncharing functionality and device registration which will participate in controller functions of accounting and limit enforcements. It also define rdmacg_device structure to bind IB stack and RDMA cgroup controller. RDMA resources are tracked using resource pool. Resource pool is per device, per cgroup entity which allows setting up accounting limits on per device basis. Resources are not defined by the RDMA cgroup, instead they are defined by the external module IB stack. This allows extending IB stack without changing kernel, as IB stack is going through changes and enhancements. Resource pool is created/destroyed dynamically whenever charging/uncharging occurs respectively and whenever user configuration is done. Its a tradeoff of memory vs little more code space that creates resource pool whenever necessary, instead of creating them during cgroup creation and device registration time. Signed-off-by: Parav Pandit <pandit.parav@gmail.com> --- include/linux/cgroup_rdma.h | 52 +++ include/linux/cgroup_subsys.h | 4 + init/Kconfig | 10 + kernel/Makefile | 1 + kernel/cgroup_rdma.c | 746 ++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 813 insertions(+) create mode 100644 include/linux/cgroup_rdma.h create mode 100644 kernel/cgroup_rdma.c