diff options
| author | Hui Zhu <zhuhui@kylinos.cn> | 2026-04-29 16:42:16 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-05-28 21:05:00 -0700 |
| commit | 838376c60df0f28b5b3659a3ef649f07d0eeadf6 (patch) | |
| tree | 77f303c2a8aa8d2905dffe105817cc4bec7a0367 /mm | |
| parent | d94d0f9c153f8d9a234171d1ff1c48e513254e7a (diff) | |
| download | linux-next-history-838376c60df0f28b5b3659a3ef649f07d0eeadf6.tar.gz | |
mm/memcontrol: hoist pstatc_pcpu assignment out of CPU loop
In mem_cgroup_alloc(), the assignment of pstatc_pcpu is invariant with
respect to the for_each_possible_cpu() loop: both the 'parent' pointer and
'parent->vmstats_percpu' remain constant throughout all iterations.
The original code redundantly re-evaluated the 'if (parent)' condition and
reassigned pstatc_pcpu on every CPU iteration, then repeated the same
ternary check 'parent ? pstatc_pcpu : NULL' when storing into
statc->parent_pcpu.
Move the single conditional assignment of pstatc_pcpu to before the loop,
resolving both the loop-invariant placement issue and the duplicated null
check. On systems with a large number of possible CPUs, this eliminates
repeated branch evaluation with no functional change.
No functional change intended.
Link: https://lore.kernel.org/20260429084216.186238-1-hui.zhu@linux.dev
Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
Reviewed-by: SeongJae Park <sj@kernel.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/memcontrol.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 177732fef010b..2bc9a7238939a 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4002,11 +4002,10 @@ static struct mem_cgroup *mem_cgroup_alloc(struct mem_cgroup *parent) if (!memcg1_alloc_events(memcg)) goto fail; + pstatc_pcpu = parent ? parent->vmstats_percpu : NULL; for_each_possible_cpu(cpu) { - if (parent) - pstatc_pcpu = parent->vmstats_percpu; statc = per_cpu_ptr(memcg->vmstats_percpu, cpu); - statc->parent_pcpu = parent ? pstatc_pcpu : NULL; + statc->parent_pcpu = pstatc_pcpu; statc->vmstats = memcg->vmstats; } |