| Message ID | 20200811020240.1231-1-wuyun.wu@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/slub: make add_full() condition more explicit | expand |
ping :) On 2020/8/11 10:02, wuyun.wu@huawei.com wrote: > From: Abel Wu <wuyun.wu@huawei.com> > > The commit below is incomplete, as it didn't handle the add_full() part. > commit a4d3f8916c65 ("slub: remove useless kmem_cache_debug() before remove_full()") > > This patch checks for SLAB_STORE_USER instead of kmem_cache_debug(), > since that should be the only context in which we need the list_lock for > add_full(). > > Signed-off-by: Abel Wu <wuyun.wu@huawei.com> > --- > mm/slub.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index f226d66408ee..df93a5a0e9a4 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2182,7 +2182,8 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, > } > } else { > m = M_FULL; > - if (kmem_cache_debug(s) && !lock) { > +#ifdef CONFIG_SLUB_DEBUG > + if ((s->flags & SLAB_STORE_USER) && !lock) { > lock = 1; > /* > * This also ensures that the scanning of full > @@ -2191,6 +2192,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, > */ > spin_lock(&n->list_lock); > } > +#endif > } > > if (l != m) { >
On Tue, 11 Aug 2020 10:02:36 +0800 <wuyun.wu@huawei.com> wrote: > From: Abel Wu <wuyun.wu@huawei.com> > > The commit below is incomplete, as it didn't handle the add_full() part. > commit a4d3f8916c65 ("slub: remove useless kmem_cache_debug() before remove_full()") > > This patch checks for SLAB_STORE_USER instead of kmem_cache_debug(), > since that should be the only context in which we need the list_lock for > add_full(). > Does this contradict what the comment tells us? * This also ensures that the scanning of full * slabs from diagnostic functions will not see * any frozen slabs.
On 2020/8/20 3:37, Andrew Morton wrote: > On Tue, 11 Aug 2020 10:02:36 +0800 <wuyun.wu@huawei.com> wrote: > >> From: Abel Wu <wuyun.wu@huawei.com> >> >> The commit below is incomplete, as it didn't handle the add_full() part. >> commit a4d3f8916c65 ("slub: remove useless kmem_cache_debug() before remove_full()") >> >> This patch checks for SLAB_STORE_USER instead of kmem_cache_debug(), >> since that should be the only context in which we need the list_lock for >> add_full(). >> > > Does this contradict what the comment tells us? > > * This also ensures that the scanning of full > * slabs from diagnostic functions will not see > * any frozen slabs. > I don't think so. If the flag SLAB_STORE_USER is not set, the slab won't be added to the full list no matter this patch is applied or not, since the check inside add_full() will guard for that. Am I missing something here? Regards, Abel
On 8/11/20 4:02 AM, wuyun.wu@huawei.com wrote: > From: Abel Wu <wuyun.wu@huawei.com> > > The commit below is incomplete, as it didn't handle the add_full() part. > commit a4d3f8916c65 ("slub: remove useless kmem_cache_debug() before remove_full()") > > This patch checks for SLAB_STORE_USER instead of kmem_cache_debug(), > since that should be the only context in which we need the list_lock for > add_full(). > > Signed-off-by: Abel Wu <wuyun.wu@huawei.com> > --- > mm/slub.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index f226d66408ee..df93a5a0e9a4 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2182,7 +2182,8 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, > } > } else { > m = M_FULL; > - if (kmem_cache_debug(s) && !lock) { > +#ifdef CONFIG_SLUB_DEBUG > + if ((s->flags & SLAB_STORE_USER) && !lock) { > lock = 1; > /* > * This also ensures that the scanning of full > @@ -2191,6 +2192,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, > */ > spin_lock(&n->list_lock); > } > +#endif > } > > if (l != m) { > Hm I missed this, otherwise I would have suggested the following -----8<----- From 0b43c7e20c81241f4b74cdb366795fc0b94a25c9 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka <vbabka@suse.cz> Date: Fri, 16 Oct 2020 18:46:06 +0200 Subject: [PATCH] mm, slub: use kmem_cache_debug_flags() in deactivate_slab() Commit 9cf7a1118365 ("mm/slub: make add_full() condition more explicit") replaced an unnecessarily generic kmem_cache_debug(s) check with an explicit check of SLAB_STORE_USER and #ifdef CONFIG_SLUB_DEBUG. We can achieve the same specific check with the recently added kmem_cache_debug_flags() which removes the #ifdef and restores the no-branch-overhead benefit of static key check when slub debugging is not enabled. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> --- mm/slub.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 61d0d2968413..28d78238f31e 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2245,8 +2245,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, } } else { m = M_FULL; -#ifdef CONFIG_SLUB_DEBUG - if ((s->flags & SLAB_STORE_USER) && !lock) { + if (kmem_cache_debug_flags(s, SLAB_STORE_USER) && !lock) { lock = 1; /* * This also ensures that the scanning of full @@ -2255,7 +2254,6 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, */ spin_lock(&n->list_lock); } -#endif } if (l != m) {
diff --git a/mm/slub.c b/mm/slub.c index f226d66408ee..df93a5a0e9a4 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2182,7 +2182,8 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, } } else { m = M_FULL; - if (kmem_cache_debug(s) && !lock) { +#ifdef CONFIG_SLUB_DEBUG + if ((s->flags & SLAB_STORE_USER) && !lock) { lock = 1; /* * This also ensures that the scanning of full @@ -2191,6 +2192,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, */ spin_lock(&n->list_lock); } +#endif } if (l != m) {