Messages in this thread | | | Date | Wed, 16 Aug 2023 17:20:32 +0800 | Subject | Re: [PATCH 4/5] drm/ttm: introduce pool_shrink_rwsem | From | Qi Zheng <> |
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Hi Christian,
On 2023/8/16 17:14, Christian König wrote: > Am 16.08.23 um 10:34 schrieb Qi Zheng: >> 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 <zhengqi.arch@bytedance.com> >> Reviewed-by: Muchun Song <songmuchun@bytedance.com> >> --- >> drivers/gpu/drm/ttm/ttm_pool.c | 15 +++++++++++++++ >> include/linux/shrinker.h | 1 - >> mm/shrinker.c | 15 --------------- >> 3 files changed, 15 insertions(+), 16 deletions(-) >> >> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c >> b/drivers/gpu/drm/ttm/ttm_pool.c >> index cddb9151d20f..713b1c0a70e1 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(&pool_shrink_rwsem); >> spin_lock(&shrinker_lock); >> pt = list_first_entry(&shrinker_list, typeof(*pt), shrinker_list); >> list_move_tail(&pt->shrinker_list, &shrinker_list); >> @@ -329,6 +331,7 @@ static unsigned int ttm_pool_shrink(void) >> } else { >> num_pages = 0; >> } >> + up_read(&pool_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) > > Please rename that function to ttm_pool_synchronize_shrinkers().
OK, will do.
> > With that done feel free to add Reviewed-by: Christian König > <christian.koenig@amd.com> >
Thanks, Qi
> Regards, > Christian. > >> +{ >> + down_write(&pool_shrink_rwsem); >> + up_write(&pool_shrink_rwsem); >> +} >> + >> /** >> * ttm_pool_fini - Cleanup a pool >> * >> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h >> index 8dc15aa37410..6b5843c3b827 100644 >> --- a/include/linux/shrinker.h >> +++ b/include/linux/shrinker.h >> @@ -103,7 +103,6 @@ extern int __printf(2, 3) register_shrinker(struct >> shrinker *shrinker, >> const char *fmt, ...); >> extern void unregister_shrinker(struct shrinker *shrinker); >> extern void free_prealloced_shrinker(struct shrinker *shrinker); >> -extern void synchronize_shrinkers(void); >> #ifdef CONFIG_SHRINKER_DEBUG >> extern int __printf(2, 3) shrinker_debugfs_rename(struct shrinker >> *shrinker, >> diff --git a/mm/shrinker.c b/mm/shrinker.c >> index 043c87ccfab4..a16cd448b924 100644 >> --- a/mm/shrinker.c >> +++ b/mm/shrinker.c >> @@ -692,18 +692,3 @@ void unregister_shrinker(struct shrinker *shrinker) >> shrinker->nr_deferred = NULL; >> } >> EXPORT_SYMBOL(unregister_shrinker); >> - >> -/** >> - * 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(&shrinker_rwsem); >> - up_write(&shrinker_rwsem); >> -} >> -EXPORT_SYMBOL(synchronize_shrinkers); >
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