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mm/memcontrol.c: remove the redundant updating of stats_flush_threshold 

Remove the redundant updating of stats_flush_threshold.  If the global var
stats_flush_threshold has exceeded the trigger value for
__mem_cgroup_flush_stats, further increment is unnecessary.

Apply the patch and test the pts/hackbench-1.0.0 Count:4 (160 threads).

Score gain: 1.95x
Reduce CPU cycles in __mod_memcg_lruvec_state (44.88% -> 0.12%)

CPU: ICX 8380 x 2 sockets
Core number: 40 x 2 physical cores
Benchmark: pts/hackbench-1.0.0 Count:4 (160 threads)

Link: https://lkml.kernel.org/r/20220722164949.47760-1-jiebin.sun@intel.com
Signed-off-by: Jiebin Sun <jiebin.sun@intel.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Acked-by: Muchun Song <songmuchun@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Amadeusz Sawiski <amadeuszx.slawinski@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jiebin Sun 2022-07-23 00:49:49 +08:00 committed by akpm
parent 914eedcb9b
commit 873f64b791
1 changed files with 8 additions and 1 deletions
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9
mm/memcontrol.c
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@ -626,7 +626,14 @@ static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val)
x = __this_cpu_add_return(stats_updates, abs(val));
if (x > MEMCG_CHARGE_BATCH) {
atomic_add(x / MEMCG_CHARGE_BATCH, &stats_flush_threshold);
/*
* If stats_flush_threshold exceeds the threshold
* (>num_online_cpus()), cgroup stats update will be triggered
* in __mem_cgroup_flush_stats(). Increasing this var further
* is redundant and simply adds overhead in atomic update.
*/
if (atomic_read(&stats_flush_threshold) <= num_online_cpus())
atomic_add(x / MEMCG_CHARGE_BATCH, &stats_flush_threshold);
__this_cpu_write(stats_updates, 0);
}
}