cgroup: rstat: retrieve current bstat to delta directly

Instead of retrieve current bstat to cur and copy it to delta, let's use
delta directly.

This saves one copy operation and has the same code convention as
propagating delta to parent.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index 0b32fa62e93c1b1276c91d27a1df71021cd9cd25..29ea74f0eab3d499bb86cae928a12ba0d4f357a1 100644 (file)
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -315,7 +315,7 @@ static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
 {
        struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
        struct cgroup *parent = cgroup_parent(cgrp);
-       struct cgroup_base_stat cur, delta;
+       struct cgroup_base_stat delta;
        unsigned seq;
 
        /* Root-level stats are sourced from system-wide CPU stats */
@@ -325,11 +325,10 @@ static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
        /* fetch the current per-cpu values */
        do {
                seq = __u64_stats_fetch_begin(&rstatc->bsync);
-               cur = rstatc->bstat;
+               delta = rstatc->bstat;
        } while (__u64_stats_fetch_retry(&rstatc->bsync, seq));
 
        /* propagate percpu delta to global */
-       delta = cur;
        cgroup_base_stat_sub(&delta, &rstatc->last_bstat);
        cgroup_base_stat_add(&cgrp->bstat, &delta);
        cgroup_base_stat_add(&rstatc->last_bstat, &delta);