| Message ID | 20210105225817.1036378-6-shy828301@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Make shrinker's nr_deferred memcg aware | expand |
On 06.01.2021 01:58, Yang Shi wrote: > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > This approach is fine with nr_deferred at the shrinker level, but the following > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > from unregistering correctly. > > Signed-off-by: Yang Shi <shy828301@gmail.com> > --- > include/linux/shrinker.h | 7 ++++--- > mm/vmscan.c | 13 +++++++++---- > 2 files changed, 13 insertions(+), 7 deletions(-) > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > index 0f80123650e2..1eac79ce57d4 100644 > --- a/include/linux/shrinker.h > +++ b/include/linux/shrinker.h > @@ -79,13 +79,14 @@ struct shrinker { > #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > > /* Flags */ > -#define SHRINKER_NUMA_AWARE (1 << 0) > -#define SHRINKER_MEMCG_AWARE (1 << 1) > +#define SHRINKER_REGISTERED (1 << 0) > +#define SHRINKER_NUMA_AWARE (1 << 1) > +#define SHRINKER_MEMCG_AWARE (1 << 2) > /* > * It just makes sense when the shrinker is also MEMCG_AWARE for now, > * non-MEMCG_AWARE shrinker should not have this flag set. > */ > -#define SHRINKER_NONSLAB (1 << 2) > +#define SHRINKER_NONSLAB (1 << 3) > > extern int prealloc_shrinker(struct shrinker *shrinker); > extern void register_shrinker_prepared(struct shrinker *shrinker); > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 8da765a85569..9761c7c27412 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -494,6 +494,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > if (shrinker->flags & SHRINKER_MEMCG_AWARE) > idr_replace(&shrinker_idr, shrinker, shrinker->id); > #endif > + shrinker->flags |= SHRINKER_REGISTERED; In case of we introduce this new flag, we should kill old flag SHRINKER_REGISTERING, which are not needed anymore (we should you the new flag instead of that). > up_write(&shrinker_rwsem); > } > > @@ -513,13 +514,17 @@ EXPORT_SYMBOL(register_shrinker); > */ > void unregister_shrinker(struct shrinker *shrinker) > { > - if (!shrinker->nr_deferred) > - return; > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > - unregister_memcg_shrinker(shrinker); > down_write(&shrinker_rwsem); I do not think there are some users which registration may race with unregistration. So, I think we should check SHRINKER_REGISTERED unlocked similar to we used to check shrinker->nr_deferred unlocked. > + if (!(shrinker->flags & SHRINKER_REGISTERED)) { > + up_write(&shrinker_rwsem); > + return; > + } > list_del(&shrinker->list); > + shrinker->flags &= ~SHRINKER_REGISTERED; > up_write(&shrinker_rwsem); > + > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > + unregister_memcg_shrinker(shrinker); > kfree(shrinker->nr_deferred); > shrinker->nr_deferred = NULL; > } >
On Wed, Jan 6, 2021 at 2:22 AM Kirill Tkhai <ktkhai@virtuozzo.com> wrote: > > On 06.01.2021 01:58, Yang Shi wrote: > > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > > This approach is fine with nr_deferred at the shrinker level, but the following > > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > > from unregistering correctly. > > > > Signed-off-by: Yang Shi <shy828301@gmail.com> > > --- > > include/linux/shrinker.h | 7 ++++--- > > mm/vmscan.c | 13 +++++++++---- > > 2 files changed, 13 insertions(+), 7 deletions(-) > > > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > > index 0f80123650e2..1eac79ce57d4 100644 > > --- a/include/linux/shrinker.h > > +++ b/include/linux/shrinker.h > > @@ -79,13 +79,14 @@ struct shrinker { > > #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > > > > /* Flags */ > > -#define SHRINKER_NUMA_AWARE (1 << 0) > > -#define SHRINKER_MEMCG_AWARE (1 << 1) > > +#define SHRINKER_REGISTERED (1 << 0) > > +#define SHRINKER_NUMA_AWARE (1 << 1) > > +#define SHRINKER_MEMCG_AWARE (1 << 2) > > /* > > * It just makes sense when the shrinker is also MEMCG_AWARE for now, > > * non-MEMCG_AWARE shrinker should not have this flag set. > > */ > > -#define SHRINKER_NONSLAB (1 << 2) > > +#define SHRINKER_NONSLAB (1 << 3) > > > > extern int prealloc_shrinker(struct shrinker *shrinker); > > extern void register_shrinker_prepared(struct shrinker *shrinker); > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 8da765a85569..9761c7c27412 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -494,6 +494,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > > if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > idr_replace(&shrinker_idr, shrinker, shrinker->id); > > #endif > > + shrinker->flags |= SHRINKER_REGISTERED; > > In case of we introduce this new flag, we should kill old flag SHRINKER_REGISTERING, > which are not needed anymore (we should you the new flag instead of that). The only think that I'm confused with is the check in shrink_slab_memcg, it does: shrinker = idr_find(&shrinker_idr, i); if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) { When allocating idr, the shrinker is associated with SHRINKER_REGISTERING. But, shrink_slab_memcg does acquire read shrinker_rwsem, and idr_alloc is called with holding write shrinker_rwsem, so I'm supposed shrink_slab_memcg should never see shrinker is registering. If so it seems easy to remove SHRINKER_REGISTERING. We just need change that check to: !shrinker || !(shrinker->flags & SHRINKER_REGISTERED) > > up_write(&shrinker_rwsem); > > } > > > > @@ -513,13 +514,17 @@ EXPORT_SYMBOL(register_shrinker); > > */ > > void unregister_shrinker(struct shrinker *shrinker) > > { > > - if (!shrinker->nr_deferred) > > - return; > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > - unregister_memcg_shrinker(shrinker); > > down_write(&shrinker_rwsem); > > I do not think there are some users which registration may race with unregistration. > So, I think we should check SHRINKER_REGISTERED unlocked similar to we used to check > shrinker->nr_deferred unlocked. Yes, I agree. > > > + if (!(shrinker->flags & SHRINKER_REGISTERED)) { > > + up_write(&shrinker_rwsem); > > + return; > > + } > > list_del(&shrinker->list); > > + shrinker->flags &= ~SHRINKER_REGISTERED; > > up_write(&shrinker_rwsem); > > + > > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > + unregister_memcg_shrinker(shrinker); > > kfree(shrinker->nr_deferred); > > shrinker->nr_deferred = NULL; > > } > > > >
On 11.01.2021 21:17, Yang Shi wrote: > On Wed, Jan 6, 2021 at 2:22 AM Kirill Tkhai <ktkhai@virtuozzo.com> wrote: >> >> On 06.01.2021 01:58, Yang Shi wrote: >>> Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. >>> This approach is fine with nr_deferred at the shrinker level, but the following >>> patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their >>> shrinker->nr_deferred would always be NULL. This would prevent the shrinkers >>> from unregistering correctly. >>> >>> Signed-off-by: Yang Shi <shy828301@gmail.com> >>> --- >>> include/linux/shrinker.h | 7 ++++--- >>> mm/vmscan.c | 13 +++++++++---- >>> 2 files changed, 13 insertions(+), 7 deletions(-) >>> >>> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h >>> index 0f80123650e2..1eac79ce57d4 100644 >>> --- a/include/linux/shrinker.h >>> +++ b/include/linux/shrinker.h >>> @@ -79,13 +79,14 @@ struct shrinker { >>> #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ >>> >>> /* Flags */ >>> -#define SHRINKER_NUMA_AWARE (1 << 0) >>> -#define SHRINKER_MEMCG_AWARE (1 << 1) >>> +#define SHRINKER_REGISTERED (1 << 0) >>> +#define SHRINKER_NUMA_AWARE (1 << 1) >>> +#define SHRINKER_MEMCG_AWARE (1 << 2) >>> /* >>> * It just makes sense when the shrinker is also MEMCG_AWARE for now, >>> * non-MEMCG_AWARE shrinker should not have this flag set. >>> */ >>> -#define SHRINKER_NONSLAB (1 << 2) >>> +#define SHRINKER_NONSLAB (1 << 3) >>> >>> extern int prealloc_shrinker(struct shrinker *shrinker); >>> extern void register_shrinker_prepared(struct shrinker *shrinker); >>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>> index 8da765a85569..9761c7c27412 100644 >>> --- a/mm/vmscan.c >>> +++ b/mm/vmscan.c >>> @@ -494,6 +494,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) >>> if (shrinker->flags & SHRINKER_MEMCG_AWARE) >>> idr_replace(&shrinker_idr, shrinker, shrinker->id); >>> #endif >>> + shrinker->flags |= SHRINKER_REGISTERED; >> >> In case of we introduce this new flag, we should kill old flag SHRINKER_REGISTERING, >> which are not needed anymore (we should you the new flag instead of that). > > The only think that I'm confused with is the check in > shrink_slab_memcg, it does: > > shrinker = idr_find(&shrinker_idr, i); > if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) { > > When allocating idr, the shrinker is associated with > SHRINKER_REGISTERING. But, shrink_slab_memcg does acquire read > shrinker_rwsem, and idr_alloc is called with holding write > shrinker_rwsem, so I'm supposed shrink_slab_memcg should never see > shrinker is registering. After prealloc_shrinker() shrinker is visible for shrink_slab_memcg(). This is the moment shrink_slab_memcg() sees SHRINKER_REGISTERED. > If so it seems easy to remove > SHRINKER_REGISTERING. > > We just need change that check to: > !shrinker || !(shrinker->flags & SHRINKER_REGISTERED) > >>> up_write(&shrinker_rwsem); >>> } >>> >>> @@ -513,13 +514,17 @@ EXPORT_SYMBOL(register_shrinker); >>> */ >>> void unregister_shrinker(struct shrinker *shrinker) >>> { >>> - if (!shrinker->nr_deferred) >>> - return; >>> - if (shrinker->flags & SHRINKER_MEMCG_AWARE) >>> - unregister_memcg_shrinker(shrinker); >>> down_write(&shrinker_rwsem); >> >> I do not think there are some users which registration may race with unregistration. >> So, I think we should check SHRINKER_REGISTERED unlocked similar to we used to check >> shrinker->nr_deferred unlocked. > > Yes, I agree. > >> >>> + if (!(shrinker->flags & SHRINKER_REGISTERED)) { >>> + up_write(&shrinker_rwsem); >>> + return; >>> + } >>> list_del(&shrinker->list); >>> + shrinker->flags &= ~SHRINKER_REGISTERED; >>> up_write(&shrinker_rwsem); >>> + >>> + if (shrinker->flags & SHRINKER_MEMCG_AWARE) >>> + unregister_memcg_shrinker(shrinker); >>> kfree(shrinker->nr_deferred); >>> shrinker->nr_deferred = NULL; >>> } >>> >> >>
On Mon, Jan 11, 2021 at 1:38 PM Kirill Tkhai <ktkhai@virtuozzo.com> wrote: > > On 11.01.2021 21:17, Yang Shi wrote: > > On Wed, Jan 6, 2021 at 2:22 AM Kirill Tkhai <ktkhai@virtuozzo.com> wrote: > >> > >> On 06.01.2021 01:58, Yang Shi wrote: > >>> Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > >>> This approach is fine with nr_deferred at the shrinker level, but the following > >>> patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > >>> shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > >>> from unregistering correctly. > >>> > >>> Signed-off-by: Yang Shi <shy828301@gmail.com> > >>> --- > >>> include/linux/shrinker.h | 7 ++++--- > >>> mm/vmscan.c | 13 +++++++++---- > >>> 2 files changed, 13 insertions(+), 7 deletions(-) > >>> > >>> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > >>> index 0f80123650e2..1eac79ce57d4 100644 > >>> --- a/include/linux/shrinker.h > >>> +++ b/include/linux/shrinker.h > >>> @@ -79,13 +79,14 @@ struct shrinker { > >>> #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > >>> > >>> /* Flags */ > >>> -#define SHRINKER_NUMA_AWARE (1 << 0) > >>> -#define SHRINKER_MEMCG_AWARE (1 << 1) > >>> +#define SHRINKER_REGISTERED (1 << 0) > >>> +#define SHRINKER_NUMA_AWARE (1 << 1) > >>> +#define SHRINKER_MEMCG_AWARE (1 << 2) > >>> /* > >>> * It just makes sense when the shrinker is also MEMCG_AWARE for now, > >>> * non-MEMCG_AWARE shrinker should not have this flag set. > >>> */ > >>> -#define SHRINKER_NONSLAB (1 << 2) > >>> +#define SHRINKER_NONSLAB (1 << 3) > >>> > >>> extern int prealloc_shrinker(struct shrinker *shrinker); > >>> extern void register_shrinker_prepared(struct shrinker *shrinker); > >>> diff --git a/mm/vmscan.c b/mm/vmscan.c > >>> index 8da765a85569..9761c7c27412 100644 > >>> --- a/mm/vmscan.c > >>> +++ b/mm/vmscan.c > >>> @@ -494,6 +494,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > >>> if (shrinker->flags & SHRINKER_MEMCG_AWARE) > >>> idr_replace(&shrinker_idr, shrinker, shrinker->id); > >>> #endif > >>> + shrinker->flags |= SHRINKER_REGISTERED; > >> > >> In case of we introduce this new flag, we should kill old flag SHRINKER_REGISTERING, > >> which are not needed anymore (we should you the new flag instead of that). > > > > The only think that I'm confused with is the check in > > shrink_slab_memcg, it does: > > > > shrinker = idr_find(&shrinker_idr, i); > > if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) { > > > > When allocating idr, the shrinker is associated with > > SHRINKER_REGISTERING. But, shrink_slab_memcg does acquire read > > shrinker_rwsem, and idr_alloc is called with holding write > > shrinker_rwsem, so I'm supposed shrink_slab_memcg should never see > > shrinker is registering. > > After prealloc_shrinker() shrinker is visible for shrink_slab_memcg(). > This is the moment shrink_slab_memcg() sees SHRINKER_REGISTERED. Yes, this exactly is what I'm supposed. > > > If so it seems easy to remove > > SHRINKER_REGISTERING. > > > > We just need change that check to: > > !shrinker || !(shrinker->flags & SHRINKER_REGISTERED) > > > >>> up_write(&shrinker_rwsem); > >>> } > >>> > >>> @@ -513,13 +514,17 @@ EXPORT_SYMBOL(register_shrinker); > >>> */ > >>> void unregister_shrinker(struct shrinker *shrinker) > >>> { > >>> - if (!shrinker->nr_deferred) > >>> - return; > >>> - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > >>> - unregister_memcg_shrinker(shrinker); > >>> down_write(&shrinker_rwsem); > >> > >> I do not think there are some users which registration may race with unregistration. > >> So, I think we should check SHRINKER_REGISTERED unlocked similar to we used to check > >> shrinker->nr_deferred unlocked. > > > > Yes, I agree. > > > >> > >>> + if (!(shrinker->flags & SHRINKER_REGISTERED)) { > >>> + up_write(&shrinker_rwsem); > >>> + return; > >>> + } > >>> list_del(&shrinker->list); > >>> + shrinker->flags &= ~SHRINKER_REGISTERED; > >>> up_write(&shrinker_rwsem); > >>> + > >>> + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > >>> + unregister_memcg_shrinker(shrinker); > >>> kfree(shrinker->nr_deferred); > >>> shrinker->nr_deferred = NULL; > >>> } > >>> > >> > >> > >
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index 0f80123650e2..1eac79ce57d4 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -79,13 +79,14 @@ struct shrinker { #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ /* Flags */ -#define SHRINKER_NUMA_AWARE (1 << 0) -#define SHRINKER_MEMCG_AWARE (1 << 1) +#define SHRINKER_REGISTERED (1 << 0) +#define SHRINKER_NUMA_AWARE (1 << 1) +#define SHRINKER_MEMCG_AWARE (1 << 2) /* * It just makes sense when the shrinker is also MEMCG_AWARE for now, * non-MEMCG_AWARE shrinker should not have this flag set. */ -#define SHRINKER_NONSLAB (1 << 2) +#define SHRINKER_NONSLAB (1 << 3) extern int prealloc_shrinker(struct shrinker *shrinker); extern void register_shrinker_prepared(struct shrinker *shrinker); diff --git a/mm/vmscan.c b/mm/vmscan.c index 8da765a85569..9761c7c27412 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -494,6 +494,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) if (shrinker->flags & SHRINKER_MEMCG_AWARE) idr_replace(&shrinker_idr, shrinker, shrinker->id); #endif + shrinker->flags |= SHRINKER_REGISTERED; up_write(&shrinker_rwsem); } @@ -513,13 +514,17 @@ EXPORT_SYMBOL(register_shrinker); */ void unregister_shrinker(struct shrinker *shrinker) { - if (!shrinker->nr_deferred) - return; - if (shrinker->flags & SHRINKER_MEMCG_AWARE) - unregister_memcg_shrinker(shrinker); down_write(&shrinker_rwsem); + if (!(shrinker->flags & SHRINKER_REGISTERED)) { + up_write(&shrinker_rwsem); + return; + } list_del(&shrinker->list); + shrinker->flags &= ~SHRINKER_REGISTERED; up_write(&shrinker_rwsem); + + if (shrinker->flags & SHRINKER_MEMCG_AWARE) + unregister_memcg_shrinker(shrinker); kfree(shrinker->nr_deferred); shrinker->nr_deferred = NULL; }
Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. This approach is fine with nr_deferred at the shrinker level, but the following patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their shrinker->nr_deferred would always be NULL. This would prevent the shrinkers from unregistering correctly. Signed-off-by: Yang Shi <shy828301@gmail.com> --- include/linux/shrinker.h | 7 ++++--- mm/vmscan.c | 13 +++++++++---- 2 files changed, 13 insertions(+), 7 deletions(-)