Re: [Cluster-devel] [PATCH v4 43/48] drm/ttm: introduce pool_shrink_rwsem
Hi Daniel, On 2023/8/22 21:56, Daniel Vetter wrote: On Mon, Aug 07, 2023 at 07:09:31PM +0800, Qi Zheng wrote: Currently, the synchronize_shrinkers() is only used by TTM pool. It only requires that no shrinkers run in parallel. After we use RCU+refcount method to implement the lockless slab shrink, we can not use shrinker_rwsem or synchronize_rcu() to guarantee that all shrinker invocations have seen an update before freeing memory. So we introduce a new pool_shrink_rwsem to implement a private synchronize_shrinkers(), so as to achieve the same purpose. Signed-off-by: Qi Zheng Reviewed-by: Muchun Song On the 5 drm patches (I counted 2 ttm and 3 drivers) for merging through some other tree (since I'm assuming that's how this will land): Yeah, there are 5 drm patches: PATCH v4 07/48 23/48 24/48 25/48 43/48. Acked-by: Daniel Vetter Thanks for your review! Qi --- drivers/gpu/drm/ttm/ttm_pool.c | 15 +++ include/linux/shrinker.h | 2 -- mm/shrinker.c | 15 --- 3 files changed, 15 insertions(+), 17 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c index c9c9618c0dce..38b4c280725c 100644 --- a/drivers/gpu/drm/ttm/ttm_pool.c +++ b/drivers/gpu/drm/ttm/ttm_pool.c @@ -74,6 +74,7 @@ static struct ttm_pool_type global_dma32_uncached[MAX_ORDER + 1]; static spinlock_t shrinker_lock; static struct list_head shrinker_list; static struct shrinker *mm_shrinker; +static DECLARE_RWSEM(pool_shrink_rwsem); /* Allocate pages of size 1 << order with the given gfp_flags */ static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t gfp_flags, @@ -317,6 +318,7 @@ static unsigned int ttm_pool_shrink(void) unsigned int num_pages; struct page *p; + down_read(_shrink_rwsem); spin_lock(_lock); pt = list_first_entry(_list, typeof(*pt), shrinker_list); list_move_tail(>shrinker_list, _list); @@ -329,6 +331,7 @@ static unsigned int ttm_pool_shrink(void) } else { num_pages = 0; } + up_read(_shrink_rwsem); return num_pages; } @@ -572,6 +575,18 @@ void ttm_pool_init(struct ttm_pool *pool, struct device *dev, } EXPORT_SYMBOL(ttm_pool_init); +/** + * synchronize_shrinkers - Wait for all running shrinkers to complete. + * + * This is useful to guarantee that all shrinker invocations have seen an + * update, before freeing memory, similar to rcu. + */ +static void synchronize_shrinkers(void) +{ + down_write(_shrink_rwsem); + up_write(_shrink_rwsem); +} + /** * ttm_pool_fini - Cleanup a pool * diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index c55c07c3f0cb..025c8070dd86 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -103,8 +103,6 @@ struct shrinker *shrinker_alloc(unsigned int flags, const char *fmt, ...); void shrinker_register(struct shrinker *shrinker); void shrinker_free(struct shrinker *shrinker); -extern void synchronize_shrinkers(void); - #ifdef CONFIG_SHRINKER_DEBUG extern int __printf(2, 3) shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...); diff --git a/mm/shrinker.c b/mm/shrinker.c index 3ab301ff122d..a27779ed3798 100644 --- a/mm/shrinker.c +++ b/mm/shrinker.c @@ -650,18 +650,3 @@ void shrinker_free(struct shrinker *shrinker) kfree(shrinker); } EXPORT_SYMBOL_GPL(shrinker_free); - -/** - * synchronize_shrinkers - Wait for all running shrinkers to complete. - * - * This is equivalent to calling unregister_shrink() and register_shrinker(), - * but atomically and with less overhead. This is useful to guarantee that all - * shrinker invocations have seen an update, before freeing memory, similar to - * rcu. - */ -void synchronize_shrinkers(void) -{ - down_write(_rwsem); - up_write(_rwsem); -} -EXPORT_SYMBOL(synchronize_shrinkers); -- 2.30.2
Re: [Cluster-devel] [PATCH v4 43/48] drm/ttm: introduce pool_shrink_rwsem
On Mon, Aug 07, 2023 at 07:09:31PM +0800, Qi Zheng wrote: > Currently, the synchronize_shrinkers() is only used by TTM pool. It only > requires that no shrinkers run in parallel. > > After we use RCU+refcount method to implement the lockless slab shrink, > we can not use shrinker_rwsem or synchronize_rcu() to guarantee that all > shrinker invocations have seen an update before freeing memory. > > So we introduce a new pool_shrink_rwsem to implement a private > synchronize_shrinkers(), so as to achieve the same purpose. > > Signed-off-by: Qi Zheng > Reviewed-by: Muchun Song On the 5 drm patches (I counted 2 ttm and 3 drivers) for merging through some other tree (since I'm assuming that's how this will land): Acked-by: Daniel Vetter > --- > drivers/gpu/drm/ttm/ttm_pool.c | 15 +++ > include/linux/shrinker.h | 2 -- > mm/shrinker.c | 15 --- > 3 files changed, 15 insertions(+), 17 deletions(-) > > diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c > index c9c9618c0dce..38b4c280725c 100644 > --- a/drivers/gpu/drm/ttm/ttm_pool.c > +++ b/drivers/gpu/drm/ttm/ttm_pool.c > @@ -74,6 +74,7 @@ static struct ttm_pool_type global_dma32_uncached[MAX_ORDER > + 1]; > static spinlock_t shrinker_lock; > static struct list_head shrinker_list; > static struct shrinker *mm_shrinker; > +static DECLARE_RWSEM(pool_shrink_rwsem); > > /* Allocate pages of size 1 << order with the given gfp_flags */ > static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t > gfp_flags, > @@ -317,6 +318,7 @@ static unsigned int ttm_pool_shrink(void) > unsigned int num_pages; > struct page *p; > > + down_read(_shrink_rwsem); > spin_lock(_lock); > pt = list_first_entry(_list, typeof(*pt), shrinker_list); > list_move_tail(>shrinker_list, _list); > @@ -329,6 +331,7 @@ static unsigned int ttm_pool_shrink(void) > } else { > num_pages = 0; > } > + up_read(_shrink_rwsem); > > return num_pages; > } > @@ -572,6 +575,18 @@ void ttm_pool_init(struct ttm_pool *pool, struct device > *dev, > } > EXPORT_SYMBOL(ttm_pool_init); > > +/** > + * synchronize_shrinkers - Wait for all running shrinkers to complete. > + * > + * This is useful to guarantee that all shrinker invocations have seen an > + * update, before freeing memory, similar to rcu. > + */ > +static void synchronize_shrinkers(void) > +{ > + down_write(_shrink_rwsem); > + up_write(_shrink_rwsem); > +} > + > /** > * ttm_pool_fini - Cleanup a pool > * > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > index c55c07c3f0cb..025c8070dd86 100644 > --- a/include/linux/shrinker.h > +++ b/include/linux/shrinker.h > @@ -103,8 +103,6 @@ struct shrinker *shrinker_alloc(unsigned int flags, const > char *fmt, ...); > void shrinker_register(struct shrinker *shrinker); > void shrinker_free(struct shrinker *shrinker); > > -extern void synchronize_shrinkers(void); > - > #ifdef CONFIG_SHRINKER_DEBUG > extern int __printf(2, 3) shrinker_debugfs_rename(struct shrinker *shrinker, > const char *fmt, ...); > diff --git a/mm/shrinker.c b/mm/shrinker.c > index 3ab301ff122d..a27779ed3798 100644 > --- a/mm/shrinker.c > +++ b/mm/shrinker.c > @@ -650,18 +650,3 @@ void shrinker_free(struct shrinker *shrinker) > kfree(shrinker); > } > EXPORT_SYMBOL_GPL(shrinker_free); > - > -/** > - * synchronize_shrinkers - Wait for all running shrinkers to complete. > - * > - * This is equivalent to calling unregister_shrink() and register_shrinker(), > - * but atomically and with less overhead. This is useful to guarantee that > all > - * shrinker invocations have seen an update, before freeing memory, similar > to > - * rcu. > - */ > -void synchronize_shrinkers(void) > -{ > - down_write(_rwsem); > - up_write(_rwsem); > -} > -EXPORT_SYMBOL(synchronize_shrinkers); > -- > 2.30.2 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch