| Message ID | 20220923155542.1212814-4-vschneid@redhat.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | sched, net: NUMA-aware CPU spreading interface | expand |
On Fri, Sep 23, 2022 at 04:55:40PM +0100, Valentin Schneider wrote: > Tariq has pointed out that drivers allocating IRQ vectors would benefit > from having smarter NUMA-awareness - cpumask_local_spread() only knows > about the local node and everything outside is in the same bucket. > > sched_domains_numa_masks is pretty much what we want to hand out (a cpumask > of CPUs reachable within a given distance budget), introduce > sched_numa_hop_mask() to export those cpumasks. > > Link: http://lore.kernel.org/r/20220728191203.4055-1-tariqt@nvidia.com > Signed-off-by: Valentin Schneider <vschneid@redhat.com> > --- > include/linux/topology.h | 12 ++++++++++++ > kernel/sched/topology.c | 31 +++++++++++++++++++++++++++++++ > 2 files changed, 43 insertions(+) > > diff --git a/include/linux/topology.h b/include/linux/topology.h > index 4564faafd0e1..3e91ae6d0ad5 100644 > --- a/include/linux/topology.h > +++ b/include/linux/topology.h > @@ -245,5 +245,17 @@ static inline const struct cpumask *cpu_cpu_mask(int cpu) > return cpumask_of_node(cpu_to_node(cpu)); > } > > +#ifdef CONFIG_NUMA > +extern const struct cpumask *sched_numa_hop_mask(int node, int hops); > +#else > +static inline const struct cpumask *sched_numa_hop_mask(int node, int hops) > +{ > + if (node == NUMA_NO_NODE && !hops) > + return cpu_online_mask; > + > + return ERR_PTR(-EOPNOTSUPP); > +} > +#endif /* CONFIG_NUMA */ > + > > #endif /* _LINUX_TOPOLOGY_H */ > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index 8739c2a5a54e..ee77706603c0 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -2067,6 +2067,37 @@ int sched_numa_find_closest(const struct cpumask *cpus, int cpu) > return found; > } > > +/** > + * sched_numa_hop_mask() - Get the cpumask of CPUs at most @hops hops away. > + * @node: The node to count hops from. > + * @hops: Include CPUs up to that many hops away. 0 means local node. > + * > + * Requires rcu_lock to be held. Returned cpumask is only valid within that > + * read-side section, copy it if required beyond that. > + * > + * Note that not all hops are equal in distance; see sched_init_numa() for how > + * distances and masks are handled. > + * > + * Also note that this is a reflection of sched_domains_numa_masks, which may change > + * during the lifetime of the system (offline nodes are taken out of the masks). > + */ Since it's exported, can you declare function parameters and return values properly? > +const struct cpumask *sched_numa_hop_mask(int node, int hops) > +{ > + struct cpumask ***masks = rcu_dereference(sched_domains_numa_masks); > + > + if (node == NUMA_NO_NODE && !hops) > + return cpu_online_mask; > + > + if (node >= nr_node_ids || hops >= sched_domains_numa_levels) > + return ERR_PTR(-EINVAL); > + > + if (!masks) > + return NULL; > + > + return masks[hops][node]; > +} > +EXPORT_SYMBOL_GPL(sched_numa_hop_mask); > + > #endif /* CONFIG_NUMA */ > > static int __sdt_alloc(const struct cpumask *cpu_map) > -- > 2.31.1
On Sun, Sep 25, 2022 at 08:00:49AM -0700, Yury Norov wrote: > On Fri, Sep 23, 2022 at 04:55:40PM +0100, Valentin Schneider wrote: > > Tariq has pointed out that drivers allocating IRQ vectors would benefit > > from having smarter NUMA-awareness - cpumask_local_spread() only knows > > about the local node and everything outside is in the same bucket. > > > > sched_domains_numa_masks is pretty much what we want to hand out (a cpumask > > of CPUs reachable within a given distance budget), introduce > > sched_numa_hop_mask() to export those cpumasks. > > > > Link: http://lore.kernel.org/r/20220728191203.4055-1-tariqt@nvidia.com > > Signed-off-by: Valentin Schneider <vschneid@redhat.com> > > --- > > include/linux/topology.h | 12 ++++++++++++ > > kernel/sched/topology.c | 31 +++++++++++++++++++++++++++++++ > > 2 files changed, 43 insertions(+) > > > > diff --git a/include/linux/topology.h b/include/linux/topology.h > > index 4564faafd0e1..3e91ae6d0ad5 100644 > > --- a/include/linux/topology.h > > +++ b/include/linux/topology.h > > @@ -245,5 +245,17 @@ static inline const struct cpumask *cpu_cpu_mask(int cpu) > > return cpumask_of_node(cpu_to_node(cpu)); > > } > > > > +#ifdef CONFIG_NUMA > > +extern const struct cpumask *sched_numa_hop_mask(int node, int hops); > > +#else > > +static inline const struct cpumask *sched_numa_hop_mask(int node, int hops) > > +{ > > + if (node == NUMA_NO_NODE && !hops) > > + return cpu_online_mask; > > + > > + return ERR_PTR(-EOPNOTSUPP); > > +} > > +#endif /* CONFIG_NUMA */ > > + > > > > #endif /* _LINUX_TOPOLOGY_H */ > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > > index 8739c2a5a54e..ee77706603c0 100644 > > --- a/kernel/sched/topology.c > > +++ b/kernel/sched/topology.c > > @@ -2067,6 +2067,37 @@ int sched_numa_find_closest(const struct cpumask *cpus, int cpu) > > return found; > > } > > > > +/** > > + * sched_numa_hop_mask() - Get the cpumask of CPUs at most @hops hops away. > > + * @node: The node to count hops from. > > + * @hops: Include CPUs up to that many hops away. 0 means local node. > > + * > > + * Requires rcu_lock to be held. Returned cpumask is only valid within that > > + * read-side section, copy it if required beyond that. > > + * > > + * Note that not all hops are equal in distance; see sched_init_numa() for how > > + * distances and masks are handled. > > + * > > + * Also note that this is a reflection of sched_domains_numa_masks, which may change > > + * during the lifetime of the system (offline nodes are taken out of the masks). > > + */ > > Since it's exported, can you declare function parameters and return > values properly? s/declare/describe
On Fri, Sep 23, 2022 at 04:55:40PM +0100, Valentin Schneider wrote: > Tariq has pointed out that drivers allocating IRQ vectors would benefit > from having smarter NUMA-awareness - cpumask_local_spread() only knows > about the local node and everything outside is in the same bucket. > > sched_domains_numa_masks is pretty much what we want to hand out (a cpumask > of CPUs reachable within a given distance budget), introduce > sched_numa_hop_mask() to export those cpumasks. > > Link: http://lore.kernel.org/r/20220728191203.4055-1-tariqt@nvidia.com > Signed-off-by: Valentin Schneider <vschneid@redhat.com> > --- > include/linux/topology.h | 12 ++++++++++++ > kernel/sched/topology.c | 31 +++++++++++++++++++++++++++++++ > 2 files changed, 43 insertions(+) > > diff --git a/include/linux/topology.h b/include/linux/topology.h > index 4564faafd0e1..3e91ae6d0ad5 100644 > --- a/include/linux/topology.h > +++ b/include/linux/topology.h > @@ -245,5 +245,17 @@ static inline const struct cpumask *cpu_cpu_mask(int cpu) > return cpumask_of_node(cpu_to_node(cpu)); > } > > +#ifdef CONFIG_NUMA > +extern const struct cpumask *sched_numa_hop_mask(int node, int hops); > +#else > +static inline const struct cpumask *sched_numa_hop_mask(int node, int hops) > +{ > + if (node == NUMA_NO_NODE && !hops) > + return cpu_online_mask; > + > + return ERR_PTR(-EOPNOTSUPP); > +} > +#endif /* CONFIG_NUMA */ > + > > #endif /* _LINUX_TOPOLOGY_H */ > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index 8739c2a5a54e..ee77706603c0 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -2067,6 +2067,37 @@ int sched_numa_find_closest(const struct cpumask *cpus, int cpu) > return found; > } > > +/** > + * sched_numa_hop_mask() - Get the cpumask of CPUs at most @hops hops away. > + * @node: The node to count hops from. > + * @hops: Include CPUs up to that many hops away. 0 means local node. > + * > + * Requires rcu_lock to be held. Returned cpumask is only valid within that > + * read-side section, copy it if required beyond that. > + * > + * Note that not all hops are equal in distance; see sched_init_numa() for how > + * distances and masks are handled. > + * > + * Also note that this is a reflection of sched_domains_numa_masks, which may change > + * during the lifetime of the system (offline nodes are taken out of the masks). > + */ > +const struct cpumask *sched_numa_hop_mask(int node, int hops) > +{ > + struct cpumask ***masks = rcu_dereference(sched_domains_numa_masks); > + > + if (node == NUMA_NO_NODE && !hops) > + return cpu_online_mask; > + > + if (node >= nr_node_ids || hops >= sched_domains_numa_levels) > + return ERR_PTR(-EINVAL); This looks like a sanity check. If so, it should go before the snippet above, so that client code would behave consistently. > + > + if (!masks) > + return NULL; In (node == NUMA_NO_NODE && !hops) case you return online cpus. Here you return NULL just to convert it to cpu_online_mask in the caller. This looks inconsistent. So, together with the above comment, this makes me feel that you'd do it like this: const struct cpumask *sched_numa_hop_mask(int node, int hops) { struct cpumask ***masks; if (node >= nr_node_ids || hops >= sched_domains_numa_levels) { #ifdef CONFIG_SCHED_DEBUG pr_err(...); #endif return ERR_PTR(-EINVAL); } if (node == NUMA_NO_NODE && !hops) return cpu_online_mask; /* or NULL */ masks = rcu_dereference(sched_domains_numa_masks); if (!masks) return cpu_online_mask; /* or NULL */ return masks[hops][node]; }
On Sun, Sep 25, 2022 at 11:05:18AM -0700, Yury Norov wrote: > On Fri, Sep 23, 2022 at 04:55:40PM +0100, Valentin Schneider wrote: > > Tariq has pointed out that drivers allocating IRQ vectors would benefit > > from having smarter NUMA-awareness - cpumask_local_spread() only knows > > about the local node and everything outside is in the same bucket. > > > > sched_domains_numa_masks is pretty much what we want to hand out (a cpumask > > of CPUs reachable within a given distance budget), introduce > > sched_numa_hop_mask() to export those cpumasks. > > > > Link: http://lore.kernel.org/r/20220728191203.4055-1-tariqt@nvidia.com > > Signed-off-by: Valentin Schneider <vschneid@redhat.com> > > --- > > include/linux/topology.h | 12 ++++++++++++ > > kernel/sched/topology.c | 31 +++++++++++++++++++++++++++++++ > > 2 files changed, 43 insertions(+) > > > > diff --git a/include/linux/topology.h b/include/linux/topology.h > > index 4564faafd0e1..3e91ae6d0ad5 100644 > > --- a/include/linux/topology.h > > +++ b/include/linux/topology.h > > @@ -245,5 +245,17 @@ static inline const struct cpumask *cpu_cpu_mask(int cpu) > > return cpumask_of_node(cpu_to_node(cpu)); > > } > > > > +#ifdef CONFIG_NUMA > > +extern const struct cpumask *sched_numa_hop_mask(int node, int hops); > > +#else > > +static inline const struct cpumask *sched_numa_hop_mask(int node, int hops) > > +{ > > + if (node == NUMA_NO_NODE && !hops) > > + return cpu_online_mask; > > + > > + return ERR_PTR(-EOPNOTSUPP); > > +} > > +#endif /* CONFIG_NUMA */ > > + > > > > #endif /* _LINUX_TOPOLOGY_H */ > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > > index 8739c2a5a54e..ee77706603c0 100644 > > --- a/kernel/sched/topology.c > > +++ b/kernel/sched/topology.c > > @@ -2067,6 +2067,37 @@ int sched_numa_find_closest(const struct cpumask *cpus, int cpu) > > return found; > > } > > > > +/** > > + * sched_numa_hop_mask() - Get the cpumask of CPUs at most @hops hops away. > > + * @node: The node to count hops from. > > + * @hops: Include CPUs up to that many hops away. 0 means local node. > > + * > > + * Requires rcu_lock to be held. Returned cpumask is only valid within that > > + * read-side section, copy it if required beyond that. > > + * > > + * Note that not all hops are equal in distance; see sched_init_numa() for how > > + * distances and masks are handled. > > + * > > + * Also note that this is a reflection of sched_domains_numa_masks, which may change > > + * during the lifetime of the system (offline nodes are taken out of the masks). > > + */ > > +const struct cpumask *sched_numa_hop_mask(int node, int hops) > > +{ > > + struct cpumask ***masks = rcu_dereference(sched_domains_numa_masks); > > + > > + if (node == NUMA_NO_NODE && !hops) > > + return cpu_online_mask; > > + > > + if (node >= nr_node_ids || hops >= sched_domains_numa_levels) > > + return ERR_PTR(-EINVAL); > > This looks like a sanity check. If so, it should go before the snippet > above, so that client code would behave consistently. > > > + > > + if (!masks) > > + return NULL; > > In (node == NUMA_NO_NODE && !hops) case you return online cpus. Here > you return NULL just to convert it to cpu_online_mask in the caller. > This looks inconsistent. So, together with the above comment, this > makes me feel that you'd do it like this: > > const struct cpumask *sched_numa_hop_mask(int node, int hops) > { > struct cpumask ***masks; > > if (node >= nr_node_ids || hops >= sched_domains_numa_levels) > { > #ifdef CONFIG_SCHED_DEBUG > pr_err(...); > #endif > return ERR_PTR(-EINVAL); > } It's an exported function, and any lame driver may crash the system by dereferencing a random pointer. You need to check the node for -2, -3, etc, because only -1 is a valid negative value. For hops, it should be an unsigned int. Right? > > if (node == NUMA_NO_NODE && !hops) > return cpu_online_mask; /* or NULL */ > > masks = rcu_dereference(sched_domains_numa_masks); > if (!masks) > return cpu_online_mask; /* or NULL */ > > return masks[hops][node]; > }
On 25/09/22 08:00, Yury Norov wrote: > On Fri, Sep 23, 2022 at 04:55:40PM +0100, Valentin Schneider wrote: >> +/** >> + * sched_numa_hop_mask() - Get the cpumask of CPUs at most @hops hops away. >> + * @node: The node to count hops from. >> + * @hops: Include CPUs up to that many hops away. 0 means local node. >> + * >> + * Requires rcu_lock to be held. Returned cpumask is only valid within that >> + * read-side section, copy it if required beyond that. >> + * >> + * Note that not all hops are equal in distance; see sched_init_numa() for how >> + * distances and masks are handled. >> + * >> + * Also note that this is a reflection of sched_domains_numa_masks, which may change >> + * during the lifetime of the system (offline nodes are taken out of the masks). >> + */ > > Since it's exported, can you declare function parameters and return > values properly? > I'll add a bit about the return value; what is missing for the parameters?
On 25/09/22 11:05, Yury Norov wrote: > On Fri, Sep 23, 2022 at 04:55:40PM +0100, Valentin Schneider wrote: >> +const struct cpumask *sched_numa_hop_mask(int node, int hops) >> +{ >> + struct cpumask ***masks = rcu_dereference(sched_domains_numa_masks); >> + >> + if (node == NUMA_NO_NODE && !hops) >> + return cpu_online_mask; >> + >> + if (node >= nr_node_ids || hops >= sched_domains_numa_levels) >> + return ERR_PTR(-EINVAL); > > This looks like a sanity check. If so, it should go before the snippet > above, so that client code would behave consistently. > nr_node_ids is unsigned, so -1 >= nr_node_ids is true. >> + >> + if (!masks) >> + return NULL; > > In (node == NUMA_NO_NODE && !hops) case you return online cpus. Here > you return NULL just to convert it to cpu_online_mask in the caller. > This looks inconsistent. So, together with the above comment, this > makes me feel that you'd do it like this: > > const struct cpumask *sched_numa_hop_mask(int node, int hops) > { > struct cpumask ***masks; > > if (node >= nr_node_ids || hops >= sched_domains_numa_levels) > { > #ifdef CONFIG_SCHED_DEBUG > pr_err(...); > #endif > return ERR_PTR(-EINVAL); > } > > if (node == NUMA_NO_NODE && !hops) > return cpu_online_mask; /* or NULL */ > > masks = rcu_dereference(sched_domains_numa_masks); > if (!masks) > return cpu_online_mask; /* or NULL */ > > return masks[hops][node]; > } If we're being pedantic, sched_numa_hop_mask() shouldn't return cpu_online_mask in those cases, but that was the least horrible option I found to get something sensible for the NUMA_NO_NODE / !CONFIG_NUMA case. I might be able to better handle this with your suggestion of having a mask iterator.
On Tue, Sep 27, 2022 at 05:45:10PM +0100, Valentin Schneider wrote: > On 25/09/22 08:00, Yury Norov wrote: > > On Fri, Sep 23, 2022 at 04:55:40PM +0100, Valentin Schneider wrote: > >> +/** > >> + * sched_numa_hop_mask() - Get the cpumask of CPUs at most @hops hops away. > >> + * @node: The node to count hops from. > >> + * @hops: Include CPUs up to that many hops away. 0 means local node. > >> + * > >> + * Requires rcu_lock to be held. Returned cpumask is only valid within that > >> + * read-side section, copy it if required beyond that. > >> + * > >> + * Note that not all hops are equal in distance; see sched_init_numa() for how > >> + * distances and masks are handled. > >> + * > >> + * Also note that this is a reflection of sched_domains_numa_masks, which may change > >> + * during the lifetime of the system (offline nodes are taken out of the masks). > >> + */ > > > > Since it's exported, can you declare function parameters and return > > values properly? > > > > I'll add a bit about the return value; what is missing for the parameters? My bad, scratch this.
diff --git a/include/linux/topology.h b/include/linux/topology.h index 4564faafd0e1..3e91ae6d0ad5 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -245,5 +245,17 @@ static inline const struct cpumask *cpu_cpu_mask(int cpu) return cpumask_of_node(cpu_to_node(cpu)); } +#ifdef CONFIG_NUMA +extern const struct cpumask *sched_numa_hop_mask(int node, int hops); +#else +static inline const struct cpumask *sched_numa_hop_mask(int node, int hops) +{ + if (node == NUMA_NO_NODE && !hops) + return cpu_online_mask; + + return ERR_PTR(-EOPNOTSUPP); +} +#endif /* CONFIG_NUMA */ + #endif /* _LINUX_TOPOLOGY_H */ diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 8739c2a5a54e..ee77706603c0 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -2067,6 +2067,37 @@ int sched_numa_find_closest(const struct cpumask *cpus, int cpu) return found; } +/** + * sched_numa_hop_mask() - Get the cpumask of CPUs at most @hops hops away. + * @node: The node to count hops from. + * @hops: Include CPUs up to that many hops away. 0 means local node. + * + * Requires rcu_lock to be held. Returned cpumask is only valid within that + * read-side section, copy it if required beyond that. + * + * Note that not all hops are equal in distance; see sched_init_numa() for how + * distances and masks are handled. + * + * Also note that this is a reflection of sched_domains_numa_masks, which may change + * during the lifetime of the system (offline nodes are taken out of the masks). + */ +const struct cpumask *sched_numa_hop_mask(int node, int hops) +{ + struct cpumask ***masks = rcu_dereference(sched_domains_numa_masks); + + if (node == NUMA_NO_NODE && !hops) + return cpu_online_mask; + + if (node >= nr_node_ids || hops >= sched_domains_numa_levels) + return ERR_PTR(-EINVAL); + + if (!masks) + return NULL; + + return masks[hops][node]; +} +EXPORT_SYMBOL_GPL(sched_numa_hop_mask); + #endif /* CONFIG_NUMA */ static int __sdt_alloc(const struct cpumask *cpu_map)
Tariq has pointed out that drivers allocating IRQ vectors would benefit from having smarter NUMA-awareness - cpumask_local_spread() only knows about the local node and everything outside is in the same bucket. sched_domains_numa_masks is pretty much what we want to hand out (a cpumask of CPUs reachable within a given distance budget), introduce sched_numa_hop_mask() to export those cpumasks. Link: http://lore.kernel.org/r/20220728191203.4055-1-tariqt@nvidia.com Signed-off-by: Valentin Schneider <vschneid@redhat.com> --- include/linux/topology.h | 12 ++++++++++++ kernel/sched/topology.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 43 insertions(+)