| Message ID | 20241026071145.3287517-1-shakeel.butt@linux.dev (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | memcg: workingset: remove folio_memcg_rcu usage | expand |
On Sat, Oct 26, 2024 at 1:12 AM Shakeel Butt <shakeel.butt@linux.dev> wrote: > > The function workingset_activation() is called from > folio_mark_accessed() with the guarantee that the given folio can not be > freed under us in workingset_activation(). In addition, the association > of the folio and its memcg can not be broken here because charge > migration is no more. There is no need to use folio_memcg_rcu. Simply > use folio_memcg_charged() because that is what this function cares > about. > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> > Suggested-by: Yu Zhao <yuzhao@google.com> > --- > > Andrew, please put this patch after the charge migration deprecation > series. > > include/linux/memcontrol.h | 35 ----------------------------------- > mm/workingset.c | 10 ++-------- > 2 files changed, 2 insertions(+), 43 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 932534291ca2..89a1e9f10e1b 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -443,35 +443,6 @@ static inline bool folio_memcg_charged(struct folio *folio) > return __folio_memcg(folio) != NULL; > } > > -/** > - * folio_memcg_rcu - Locklessly get the memory cgroup associated with a folio. > - * @folio: Pointer to the folio. > - * > - * This function assumes that the folio is known to have a > - * proper memory cgroup pointer. It's not safe to call this function > - * against some type of folios, e.g. slab folios or ex-slab folios. > - * > - * Return: A pointer to the memory cgroup associated with the folio, > - * or NULL. > - */ > -static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio) > -{ > - unsigned long memcg_data = READ_ONCE(folio->memcg_data); > - > - VM_BUG_ON_FOLIO(folio_test_slab(folio), folio); > - > - if (memcg_data & MEMCG_DATA_KMEM) { > - struct obj_cgroup *objcg; > - > - objcg = (void *)(memcg_data & ~OBJEXTS_FLAGS_MASK); > - return obj_cgroup_memcg(objcg); > - } > - > - WARN_ON_ONCE(!rcu_read_lock_held()); > - > - return (struct mem_cgroup *)(memcg_data & ~OBJEXTS_FLAGS_MASK); > -} > - > /* > * folio_memcg_check - Get the memory cgroup associated with a folio. > * @folio: Pointer to the folio. > @@ -1084,12 +1055,6 @@ static inline struct mem_cgroup *folio_memcg(struct folio *folio) > return NULL; > } > > -static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio) > -{ > - WARN_ON_ONCE(!rcu_read_lock_held()); > - return NULL; > -} > - > static inline struct mem_cgroup *folio_memcg_check(struct folio *folio) > { > return NULL; > diff --git a/mm/workingset.c b/mm/workingset.c > index 4b58ef535a17..c47aa482fad5 100644 > --- a/mm/workingset.c > +++ b/mm/workingset.c > @@ -591,9 +591,6 @@ void workingset_refault(struct folio *folio, void *shadow) > */ > void workingset_activation(struct folio *folio) > { > - struct mem_cgroup *memcg; > - > - rcu_read_lock(); > /* > * Filter non-memcg pages here, e.g. unmap can call > * mark_page_accessed() on VDSO pages. > @@ -601,12 +598,9 @@ void workingset_activation(struct folio *folio) > * XXX: See workingset_refault() - this should return > * root_mem_cgroup even for !CONFIG_MEMCG. The "XXX" part of the comments doesn't apply anymore. > */ > - memcg = folio_memcg_rcu(folio); > - if (!mem_cgroup_disabled() && !memcg) > - goto out; > + if (mem_cgroup_disabled() || !folio_memcg_charged(folio)) > + return; > workingset_age_nonresident(folio_lruvec(folio), folio_nr_pages(folio)); if (mem_cgroup_disabled() || folio_memcg_charged(folio)) workingset_age_nonresident() We still want to call workingset_age_nonresident() when memcg is disabled. (We just want to "Filter non-memcg pages here" when memcg is enabled, as the comment above says, which I assume still applies?) > -out: > - rcu_read_unlock(); > } > > /* > -- > 2.43.5 >
On Sat, Oct 26, 2024 at 09:37:00AM GMT, Yu Zhao wrote: > On Sat, Oct 26, 2024 at 1:12 AM Shakeel Butt <shakeel.butt@linux.dev> wrote: > > > > The function workingset_activation() is called from > > folio_mark_accessed() with the guarantee that the given folio can not be > > freed under us in workingset_activation(). In addition, the association > > of the folio and its memcg can not be broken here because charge > > migration is no more. There is no need to use folio_memcg_rcu. Simply > > use folio_memcg_charged() because that is what this function cares > > about. > > > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> > > Suggested-by: Yu Zhao <yuzhao@google.com> > > --- > > > > Andrew, please put this patch after the charge migration deprecation > > series. > > > > include/linux/memcontrol.h | 35 ----------------------------------- > > mm/workingset.c | 10 ++-------- > > 2 files changed, 2 insertions(+), 43 deletions(-) > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > index 932534291ca2..89a1e9f10e1b 100644 > > --- a/include/linux/memcontrol.h > > +++ b/include/linux/memcontrol.h > > @@ -443,35 +443,6 @@ static inline bool folio_memcg_charged(struct folio *folio) > > return __folio_memcg(folio) != NULL; > > } > > > > -/** > > - * folio_memcg_rcu - Locklessly get the memory cgroup associated with a folio. > > - * @folio: Pointer to the folio. > > - * > > - * This function assumes that the folio is known to have a > > - * proper memory cgroup pointer. It's not safe to call this function > > - * against some type of folios, e.g. slab folios or ex-slab folios. > > - * > > - * Return: A pointer to the memory cgroup associated with the folio, > > - * or NULL. > > - */ > > -static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio) > > -{ > > - unsigned long memcg_data = READ_ONCE(folio->memcg_data); > > - > > - VM_BUG_ON_FOLIO(folio_test_slab(folio), folio); > > - > > - if (memcg_data & MEMCG_DATA_KMEM) { > > - struct obj_cgroup *objcg; > > - > > - objcg = (void *)(memcg_data & ~OBJEXTS_FLAGS_MASK); > > - return obj_cgroup_memcg(objcg); > > - } > > - > > - WARN_ON_ONCE(!rcu_read_lock_held()); > > - > > - return (struct mem_cgroup *)(memcg_data & ~OBJEXTS_FLAGS_MASK); > > -} > > - > > /* > > * folio_memcg_check - Get the memory cgroup associated with a folio. > > * @folio: Pointer to the folio. > > @@ -1084,12 +1055,6 @@ static inline struct mem_cgroup *folio_memcg(struct folio *folio) > > return NULL; > > } > > > > -static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio) > > -{ > > - WARN_ON_ONCE(!rcu_read_lock_held()); > > - return NULL; > > -} > > - > > static inline struct mem_cgroup *folio_memcg_check(struct folio *folio) > > { > > return NULL; > > diff --git a/mm/workingset.c b/mm/workingset.c > > index 4b58ef535a17..c47aa482fad5 100644 > > --- a/mm/workingset.c > > +++ b/mm/workingset.c > > @@ -591,9 +591,6 @@ void workingset_refault(struct folio *folio, void *shadow) > > */ > > void workingset_activation(struct folio *folio) > > { > > - struct mem_cgroup *memcg; > > - > > - rcu_read_lock(); > > /* > > * Filter non-memcg pages here, e.g. unmap can call > > * mark_page_accessed() on VDSO pages. > > @@ -601,12 +598,9 @@ void workingset_activation(struct folio *folio) > > * XXX: See workingset_refault() - this should return > > * root_mem_cgroup even for !CONFIG_MEMCG. > > The "XXX" part of the comments doesn't apply anymore. > > > */ > > - memcg = folio_memcg_rcu(folio); > > - if (!mem_cgroup_disabled() && !memcg) > > - goto out; > > + if (mem_cgroup_disabled() || !folio_memcg_charged(folio)) > > + return; > > workingset_age_nonresident(folio_lruvec(folio), folio_nr_pages(folio)); > > if (mem_cgroup_disabled() || folio_memcg_charged(folio)) > workingset_age_nonresident() > > We still want to call workingset_age_nonresident() when memcg is > disabled. (We just want to "Filter non-memcg pages here" when memcg is > enabled, as the comment above says, which I assume still applies?) > Yes, you are right. Let me send the v2 with the fix.
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 932534291ca2..89a1e9f10e1b 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -443,35 +443,6 @@ static inline bool folio_memcg_charged(struct folio *folio) return __folio_memcg(folio) != NULL; } -/** - * folio_memcg_rcu - Locklessly get the memory cgroup associated with a folio. - * @folio: Pointer to the folio. - * - * This function assumes that the folio is known to have a - * proper memory cgroup pointer. It's not safe to call this function - * against some type of folios, e.g. slab folios or ex-slab folios. - * - * Return: A pointer to the memory cgroup associated with the folio, - * or NULL. - */ -static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio) -{ - unsigned long memcg_data = READ_ONCE(folio->memcg_data); - - VM_BUG_ON_FOLIO(folio_test_slab(folio), folio); - - if (memcg_data & MEMCG_DATA_KMEM) { - struct obj_cgroup *objcg; - - objcg = (void *)(memcg_data & ~OBJEXTS_FLAGS_MASK); - return obj_cgroup_memcg(objcg); - } - - WARN_ON_ONCE(!rcu_read_lock_held()); - - return (struct mem_cgroup *)(memcg_data & ~OBJEXTS_FLAGS_MASK); -} - /* * folio_memcg_check - Get the memory cgroup associated with a folio. * @folio: Pointer to the folio. @@ -1084,12 +1055,6 @@ static inline struct mem_cgroup *folio_memcg(struct folio *folio) return NULL; } -static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio) -{ - WARN_ON_ONCE(!rcu_read_lock_held()); - return NULL; -} - static inline struct mem_cgroup *folio_memcg_check(struct folio *folio) { return NULL; diff --git a/mm/workingset.c b/mm/workingset.c index 4b58ef535a17..c47aa482fad5 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -591,9 +591,6 @@ void workingset_refault(struct folio *folio, void *shadow) */ void workingset_activation(struct folio *folio) { - struct mem_cgroup *memcg; - - rcu_read_lock(); /* * Filter non-memcg pages here, e.g. unmap can call * mark_page_accessed() on VDSO pages. @@ -601,12 +598,9 @@ void workingset_activation(struct folio *folio) * XXX: See workingset_refault() - this should return * root_mem_cgroup even for !CONFIG_MEMCG. */ - memcg = folio_memcg_rcu(folio); - if (!mem_cgroup_disabled() && !memcg) - goto out; + if (mem_cgroup_disabled() || !folio_memcg_charged(folio)) + return; workingset_age_nonresident(folio_lruvec(folio), folio_nr_pages(folio)); -out: - rcu_read_unlock(); } /*
The function workingset_activation() is called from folio_mark_accessed() with the guarantee that the given folio can not be freed under us in workingset_activation(). In addition, the association of the folio and its memcg can not be broken here because charge migration is no more. There is no need to use folio_memcg_rcu. Simply use folio_memcg_charged() because that is what this function cares about. Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> Suggested-by: Yu Zhao <yuzhao@google.com> --- Andrew, please put this patch after the charge migration deprecation series. include/linux/memcontrol.h | 35 ----------------------------------- mm/workingset.c | 10 ++-------- 2 files changed, 2 insertions(+), 43 deletions(-)