| Message ID | 20240430060612.2171650-2-shakeel.butt@linux.dev (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | memcg: reduce memory consumption by memcg stats | expand |
On Mon, Apr 29, 2024 at 11:06 PM Shakeel Butt <shakeel.butt@linux.dev> wrote: > > mem_cgroup_events_index is a translation table to get the right index of > the memcg relevant entry for the general vm_event_item. At the moment, > it is defined as integer array. However on a typical system the max > entry of vm_event_item (NR_VM_EVENT_ITEMS) is 113, so we don't need to > use int as storage type of the array. For now just use int8_t as type > and add a BUILD_BUG_ON() and will switch to short once NR_VM_EVENT_ITEMS > touches 127. > > Another benefit of this change is that the translation table fits in 2 > cachelines while previously it would require 8 cachelines (assuming 64 > bytes cachesline). > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> > Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev> Reviewed-by: Yosry Ahmed <yosryahmed@google.com> > --- > Changes since v2: > - Used S8_MAX instead of 127 > - Update commit message based on Yosry's feedback. > > mm/memcontrol.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 602ad5faad4d..c146187cda9c 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -607,11 +607,13 @@ static const unsigned int memcg_vm_event_stat[] = { > }; > > #define NR_MEMCG_EVENTS ARRAY_SIZE(memcg_vm_event_stat) > -static int mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly; > +static int8_t mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly; > > static void init_memcg_events(void) > { > - int i; > + int8_t i; > + > + BUILD_BUG_ON(NR_VM_EVENT_ITEMS >= S8_MAX); > > for (i = 0; i < NR_MEMCG_EVENTS; ++i) > mem_cgroup_events_index[memcg_vm_event_stat[i]] = i + 1; > -- > 2.43.0 >
On Tue, Apr 30, 2024 at 1:34 AM Yosry Ahmed <yosryahmed@google.com> wrote: > > On Mon, Apr 29, 2024 at 11:06 PM Shakeel Butt <shakeel.butt@linux.dev> wrote: > > > > mem_cgroup_events_index is a translation table to get the right index of > > the memcg relevant entry for the general vm_event_item. At the moment, > > it is defined as integer array. However on a typical system the max > > entry of vm_event_item (NR_VM_EVENT_ITEMS) is 113, so we don't need to > > use int as storage type of the array. For now just use int8_t as type > > and add a BUILD_BUG_ON() and will switch to short once NR_VM_EVENT_ITEMS > > touches 127. > > > > Another benefit of this change is that the translation table fits in 2 > > cachelines while previously it would require 8 cachelines (assuming 64 > > bytes cachesline). > > > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> > > Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev> > > Reviewed-by: Yosry Ahmed <yosryahmed@google.com> > Reviewed-by: T.J. Mercier <tjmercier@google.com>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 602ad5faad4d..c146187cda9c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -607,11 +607,13 @@ static const unsigned int memcg_vm_event_stat[] = { }; #define NR_MEMCG_EVENTS ARRAY_SIZE(memcg_vm_event_stat) -static int mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly; +static int8_t mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly; static void init_memcg_events(void) { - int i; + int8_t i; + + BUILD_BUG_ON(NR_VM_EVENT_ITEMS >= S8_MAX); for (i = 0; i < NR_MEMCG_EVENTS; ++i) mem_cgroup_events_index[memcg_vm_event_stat[i]] = i + 1;