| Message ID | 152663304128.5308.12840831728812876902.stgit@localhost.localdomain (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, May 18, 2018 at 11:44:01AM +0300, Kirill Tkhai wrote: > Using the preparations made in previous patches, in case of memcg > shrink, we may avoid shrinkers, which are not set in memcg's shrinkers > bitmap. To do that, we separate iterations over memcg-aware and > !memcg-aware shrinkers, and memcg-aware shrinkers are chosen > via for_each_set_bit() from the bitmap. In case of big nodes, > having many isolated environments, this gives significant > performance growth. See next patches for the details. > > Note, that the patch does not respect to empty memcg shrinkers, > since we never clear the bitmap bits after we set it once. > Their shrinkers will be called again, with no shrinked objects > as result. This functionality is provided by next patches. > > Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> > --- > mm/vmscan.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++------ > 1 file changed, 78 insertions(+), 9 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index f09ea20d7270..2fbf3b476601 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -373,6 +373,20 @@ int prealloc_shrinker(struct shrinker *shrinker) > goto free_deferred; > } > > + /* > + * There is a window between prealloc_shrinker() > + * and register_shrinker_prepared(). We don't want > + * to clear bit of a shrinker in such the state > + * in shrink_slab_memcg(), since this will impose > + * restrictions on a code registering a shrinker > + * (they would have to guarantee, their LRU lists > + * are empty till shrinker is completely registered). > + * So, we differ the situation, when 1)a shrinker > + * is semi-registered (id is assigned, but it has > + * not yet linked to shrinker_list) and 2)shrinker > + * is not registered (id is not assigned). > + */ > + INIT_LIST_HEAD(&shrinker->list); > return 0; > > free_deferred: > @@ -544,6 +558,67 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, > return freed; > } > > +#ifdef CONFIG_MEMCG_KMEM > +static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, > + struct mem_cgroup *memcg, int priority) > +{ > + struct memcg_shrinker_map *map; > + unsigned long freed = 0; > + int ret, i; > + > + if (!memcg_kmem_enabled() || !mem_cgroup_online(memcg)) > + return 0; > + > + if (!down_read_trylock(&shrinker_rwsem)) > + return 0; > + > + /* > + * 1) Caller passes only alive memcg, so map can't be NULL. > + * 2) shrinker_rwsem protects from maps expanding. > + */ > + map = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_map, > + true); > + BUG_ON(!map); > + > + for_each_set_bit(i, map->map, memcg_shrinker_nr_max) { > + struct shrink_control sc = { > + .gfp_mask = gfp_mask, > + .nid = nid, > + .memcg = memcg, > + }; > + struct shrinker *shrinker; > + > + shrinker = idr_find(&shrinker_idr, i); > + if (unlikely(!shrinker)) { Nit: I don't think 'unlikely' is required here as this is definitely not a hot path. > + clear_bit(i, map->map); > + continue; > + } > + BUG_ON(!(shrinker->flags & SHRINKER_MEMCG_AWARE)); > + > + /* See comment in prealloc_shrinker() */ > + if (unlikely(list_empty(&shrinker->list))) Ditto. > + continue; > + > + ret = do_shrink_slab(&sc, shrinker, priority); > + freed += ret; > + > + if (rwsem_is_contended(&shrinker_rwsem)) { > + freed = freed ? : 1; > + break; > + } > + } > + > + up_read(&shrinker_rwsem); > + return freed; > +} > +#else /* CONFIG_MEMCG_KMEM */ > +static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, > + struct mem_cgroup *memcg, int priority) > +{ > + return 0; > +} > +#endif /* CONFIG_MEMCG_KMEM */ > + > /** > * shrink_slab - shrink slab caches > * @gfp_mask: allocation context > @@ -573,8 +648,8 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, > struct shrinker *shrinker; > unsigned long freed = 0; > > - if (memcg && (!memcg_kmem_enabled() || !mem_cgroup_online(memcg))) > - return 0; > + if (memcg && !mem_cgroup_is_root(memcg)) > + return shrink_slab_memcg(gfp_mask, nid, memcg, priority); > > if (!down_read_trylock(&shrinker_rwsem)) > goto out; > @@ -586,13 +661,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, > .memcg = memcg, > }; > > - /* > - * If kernel memory accounting is disabled, we ignore > - * SHRINKER_MEMCG_AWARE flag and call all shrinkers > - * passing NULL for memcg. > - */ > - if (memcg_kmem_enabled() && > - !!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE)) > + if (!!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE)) > continue; > > if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) >
On 20.05.2018 11:00, Vladimir Davydov wrote: > On Fri, May 18, 2018 at 11:44:01AM +0300, Kirill Tkhai wrote: >> Using the preparations made in previous patches, in case of memcg >> shrink, we may avoid shrinkers, which are not set in memcg's shrinkers >> bitmap. To do that, we separate iterations over memcg-aware and >> !memcg-aware shrinkers, and memcg-aware shrinkers are chosen >> via for_each_set_bit() from the bitmap. In case of big nodes, >> having many isolated environments, this gives significant >> performance growth. See next patches for the details. >> >> Note, that the patch does not respect to empty memcg shrinkers, >> since we never clear the bitmap bits after we set it once. >> Their shrinkers will be called again, with no shrinked objects >> as result. This functionality is provided by next patches. >> >> Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> >> --- >> mm/vmscan.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++------ >> 1 file changed, 78 insertions(+), 9 deletions(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index f09ea20d7270..2fbf3b476601 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -373,6 +373,20 @@ int prealloc_shrinker(struct shrinker *shrinker) >> goto free_deferred; >> } >> >> + /* >> + * There is a window between prealloc_shrinker() >> + * and register_shrinker_prepared(). We don't want >> + * to clear bit of a shrinker in such the state >> + * in shrink_slab_memcg(), since this will impose >> + * restrictions on a code registering a shrinker >> + * (they would have to guarantee, their LRU lists >> + * are empty till shrinker is completely registered). >> + * So, we differ the situation, when 1)a shrinker >> + * is semi-registered (id is assigned, but it has >> + * not yet linked to shrinker_list) and 2)shrinker >> + * is not registered (id is not assigned). >> + */ >> + INIT_LIST_HEAD(&shrinker->list); >> return 0; >> >> free_deferred: >> @@ -544,6 +558,67 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, >> return freed; >> } >> >> +#ifdef CONFIG_MEMCG_KMEM >> +static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, >> + struct mem_cgroup *memcg, int priority) >> +{ >> + struct memcg_shrinker_map *map; >> + unsigned long freed = 0; >> + int ret, i; >> + >> + if (!memcg_kmem_enabled() || !mem_cgroup_online(memcg)) >> + return 0; >> + >> + if (!down_read_trylock(&shrinker_rwsem)) >> + return 0; >> + >> + /* >> + * 1) Caller passes only alive memcg, so map can't be NULL. >> + * 2) shrinker_rwsem protects from maps expanding. >> + */ >> + map = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_map, >> + true); >> + BUG_ON(!map); >> + >> + for_each_set_bit(i, map->map, memcg_shrinker_nr_max) { >> + struct shrink_control sc = { >> + .gfp_mask = gfp_mask, >> + .nid = nid, >> + .memcg = memcg, >> + }; >> + struct shrinker *shrinker; >> + >> + shrinker = idr_find(&shrinker_idr, i); >> + if (unlikely(!shrinker)) { > > Nit: I don't think 'unlikely' is required here as this is definitely not > a hot path. In case of big machines with many containers and overcommit, shrink_slab() in general is very hot path. See the patchset description. There are configurations, when only shrink_slab() is executing and occupies cpu for 100%, it's the reason of this patchset is made for. Here is the place we are absolutely sure shrinker is NULL in case if race with parallel registering, so I don't see anything wrong to give compiler some information about branch prediction. >> + clear_bit(i, map->map); >> + continue; >> + } >> + BUG_ON(!(shrinker->flags & SHRINKER_MEMCG_AWARE)); >> + >> + /* See comment in prealloc_shrinker() */ >> + if (unlikely(list_empty(&shrinker->list))) > > Ditto. > >> + continue; >> + >> + ret = do_shrink_slab(&sc, shrinker, priority); >> + freed += ret; >> + >> + if (rwsem_is_contended(&shrinker_rwsem)) { >> + freed = freed ? : 1; >> + break; >> + } >> + } >> + >> + up_read(&shrinker_rwsem); >> + return freed; >> +} >> +#else /* CONFIG_MEMCG_KMEM */ >> +static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, >> + struct mem_cgroup *memcg, int priority) >> +{ >> + return 0; >> +} >> +#endif /* CONFIG_MEMCG_KMEM */ >> + >> /** >> * shrink_slab - shrink slab caches >> * @gfp_mask: allocation context >> @@ -573,8 +648,8 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, >> struct shrinker *shrinker; >> unsigned long freed = 0; >> >> - if (memcg && (!memcg_kmem_enabled() || !mem_cgroup_online(memcg))) >> - return 0; >> + if (memcg && !mem_cgroup_is_root(memcg)) >> + return shrink_slab_memcg(gfp_mask, nid, memcg, priority); >> >> if (!down_read_trylock(&shrinker_rwsem)) >> goto out; >> @@ -586,13 +661,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, >> .memcg = memcg, >> }; >> >> - /* >> - * If kernel memory accounting is disabled, we ignore >> - * SHRINKER_MEMCG_AWARE flag and call all shrinkers >> - * passing NULL for memcg. >> - */ >> - if (memcg_kmem_enabled() && >> - !!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE)) >> + if (!!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE)) >> continue; >> >> if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) >>
On Mon, May 21, 2018 at 12:17:07PM +0300, Kirill Tkhai wrote: > >> +static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, > >> + struct mem_cgroup *memcg, int priority) > >> +{ > >> + struct memcg_shrinker_map *map; > >> + unsigned long freed = 0; > >> + int ret, i; > >> + > >> + if (!memcg_kmem_enabled() || !mem_cgroup_online(memcg)) > >> + return 0; > >> + > >> + if (!down_read_trylock(&shrinker_rwsem)) > >> + return 0; > >> + > >> + /* > >> + * 1) Caller passes only alive memcg, so map can't be NULL. > >> + * 2) shrinker_rwsem protects from maps expanding. > >> + */ > >> + map = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_map, > >> + true); > >> + BUG_ON(!map); > >> + > >> + for_each_set_bit(i, map->map, memcg_shrinker_nr_max) { > >> + struct shrink_control sc = { > >> + .gfp_mask = gfp_mask, > >> + .nid = nid, > >> + .memcg = memcg, > >> + }; > >> + struct shrinker *shrinker; > >> + > >> + shrinker = idr_find(&shrinker_idr, i); > >> + if (unlikely(!shrinker)) { > > > > Nit: I don't think 'unlikely' is required here as this is definitely not > > a hot path. > > In case of big machines with many containers and overcommit, shrink_slab() > in general is very hot path. See the patchset description. There are configurations, > when only shrink_slab() is executing and occupies cpu for 100%, it's the reason > of this patchset is made for. > > Here is the place we are absolutely sure shrinker is NULL in case if race with parallel > registering, so I don't see anything wrong to give compiler some information about branch > prediction. OK. If you're confident this 'unlikely' is useful, let's leave it as is.
diff --git a/mm/vmscan.c b/mm/vmscan.c index f09ea20d7270..2fbf3b476601 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -373,6 +373,20 @@ int prealloc_shrinker(struct shrinker *shrinker) goto free_deferred; } + /* + * There is a window between prealloc_shrinker() + * and register_shrinker_prepared(). We don't want + * to clear bit of a shrinker in such the state + * in shrink_slab_memcg(), since this will impose + * restrictions on a code registering a shrinker + * (they would have to guarantee, their LRU lists + * are empty till shrinker is completely registered). + * So, we differ the situation, when 1)a shrinker + * is semi-registered (id is assigned, but it has + * not yet linked to shrinker_list) and 2)shrinker + * is not registered (id is not assigned). + */ + INIT_LIST_HEAD(&shrinker->list); return 0; free_deferred: @@ -544,6 +558,67 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, return freed; } +#ifdef CONFIG_MEMCG_KMEM +static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, + struct mem_cgroup *memcg, int priority) +{ + struct memcg_shrinker_map *map; + unsigned long freed = 0; + int ret, i; + + if (!memcg_kmem_enabled() || !mem_cgroup_online(memcg)) + return 0; + + if (!down_read_trylock(&shrinker_rwsem)) + return 0; + + /* + * 1) Caller passes only alive memcg, so map can't be NULL. + * 2) shrinker_rwsem protects from maps expanding. + */ + map = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_map, + true); + BUG_ON(!map); + + for_each_set_bit(i, map->map, memcg_shrinker_nr_max) { + struct shrink_control sc = { + .gfp_mask = gfp_mask, + .nid = nid, + .memcg = memcg, + }; + struct shrinker *shrinker; + + shrinker = idr_find(&shrinker_idr, i); + if (unlikely(!shrinker)) { + clear_bit(i, map->map); + continue; + } + BUG_ON(!(shrinker->flags & SHRINKER_MEMCG_AWARE)); + + /* See comment in prealloc_shrinker() */ + if (unlikely(list_empty(&shrinker->list))) + continue; + + ret = do_shrink_slab(&sc, shrinker, priority); + freed += ret; + + if (rwsem_is_contended(&shrinker_rwsem)) { + freed = freed ? : 1; + break; + } + } + + up_read(&shrinker_rwsem); + return freed; +} +#else /* CONFIG_MEMCG_KMEM */ +static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, + struct mem_cgroup *memcg, int priority) +{ + return 0; +} +#endif /* CONFIG_MEMCG_KMEM */ + /** * shrink_slab - shrink slab caches * @gfp_mask: allocation context @@ -573,8 +648,8 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct shrinker *shrinker; unsigned long freed = 0; - if (memcg && (!memcg_kmem_enabled() || !mem_cgroup_online(memcg))) - return 0; + if (memcg && !mem_cgroup_is_root(memcg)) + return shrink_slab_memcg(gfp_mask, nid, memcg, priority); if (!down_read_trylock(&shrinker_rwsem)) goto out; @@ -586,13 +661,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, .memcg = memcg, }; - /* - * If kernel memory accounting is disabled, we ignore - * SHRINKER_MEMCG_AWARE flag and call all shrinkers - * passing NULL for memcg. - */ - if (memcg_kmem_enabled() && - !!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE)) + if (!!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE)) continue; if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
Using the preparations made in previous patches, in case of memcg shrink, we may avoid shrinkers, which are not set in memcg's shrinkers bitmap. To do that, we separate iterations over memcg-aware and !memcg-aware shrinkers, and memcg-aware shrinkers are chosen via for_each_set_bit() from the bitmap. In case of big nodes, having many isolated environments, this gives significant performance growth. See next patches for the details. Note, that the patch does not respect to empty memcg shrinkers, since we never clear the bitmap bits after we set it once. Their shrinkers will be called again, with no shrinked objects as result. This functionality is provided by next patches. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> --- mm/vmscan.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 78 insertions(+), 9 deletions(-)