Messages in this thread | | | Date | Wed, 23 Aug 2023 10:59:34 +0800 | Subject | Re: [PATCH v4 43/48] drm/ttm: introduce pool_shrink_rwsem | From | Qi Zheng <> |
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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 <zhengqi.arch@bytedance.com> >> Reviewed-by: Muchun Song <songmuchun@bytedance.com> > > 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 <daniel.vetter@ffwll.ch>
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(&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) >> +{ >> + 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 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(&shrinker_rwsem); >> - up_write(&shrinker_rwsem); >> -} >> -EXPORT_SYMBOL(synchronize_shrinkers); >> -- >> 2.30.2 >> >
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