Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Shakeel Butt <> | Subject | [PATCH v3 1/8] memcg: reduce memory size of mem_cgroup_events_index | Date | Mon, 29 Apr 2024 23:06:05 -0700 |
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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> --- 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
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