cgroup: rename cgroup_rstat_flush_"irqsafe" to "atomic"

Patch series "memcg: avoid flushing stats atomically where possible", v3.

rstat flushing is an expensive operation that scales with the number of
cpus and the number of cgroups in the system.  The purpose of this series
is to minimize the contexts where we flush stats atomically.

Patches 1 and 2 are cleanups requested during reviews of prior versions of
this series.

Patch 3 makes sure we never try to flush from within an irq context.

Patches 4 to 7 introduce separate variants of mem_cgroup_flush_stats() for
atomic and non-atomic flushing, and make sure we only flush the stats
atomically when necessary.

Patch 8 is a slightly tangential optimization that limits the work done by
rstat flushing in some scenarios.

This patch (of 8):

cgroup_rstat_flush_irqsafe() can be a confusing name.  It may read as
"irqs are disabled throughout", which is what the current implementation
does (currently under discussion [1]), but is not the intention.  The
intention is that this function is safe to call from atomic contexts.
Name it as such.

Link: https://lkml.kernel.org/r/20230330191801.1967435-1-yosryahmed@google.com
Link: https://lkml.kernel.org/r/20230330191801.1967435-2-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vasily Averin <vasily.averin@linux.dev>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 3410aecffdb47757cd6410d13fc1a8df3c1d0b83..885f5395fcd04e5e5310e8c1019c0ad7ff9b2535 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -692,7 +692,7 @@ static inline void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
  */
 void cgroup_rstat_updated(struct cgroup *cgrp, int cpu);
 void cgroup_rstat_flush(struct cgroup *cgrp);
-void cgroup_rstat_flush_irqsafe(struct cgroup *cgrp);
+void cgroup_rstat_flush_atomic(struct cgroup *cgrp);
 void cgroup_rstat_flush_hold(struct cgroup *cgrp);
 void cgroup_rstat_flush_release(void);
 

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index 831f1f472bb814c945006f996d978c545e7a8759..d3252b0416b697fd9c9aab35c738942d8a9fe2a1 100644 (file)
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -241,12 +241,12 @@ __bpf_kfunc void cgroup_rstat_flush(struct cgroup *cgrp)
 }
 
 /**
- * cgroup_rstat_flush_irqsafe - irqsafe version of cgroup_rstat_flush()
+ * cgroup_rstat_flush_atomic- atomic version of cgroup_rstat_flush()
  * @cgrp: target cgroup
  *
  * This function can be called from any context.
  */
-void cgroup_rstat_flush_irqsafe(struct cgroup *cgrp)
+void cgroup_rstat_flush_atomic(struct cgroup *cgrp)
 {
        unsigned long flags;
 

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 681e7528a714e0ba191267d72b5f671187281b6b..b7c3eab6b4fe902aee8c8ee8bf3512968a518d84 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -643,7 +643,7 @@ static void __mem_cgroup_flush_stats(void)
                return;
 
        flush_next_time = jiffies_64 + 2*FLUSH_TIME;
-       cgroup_rstat_flush_irqsafe(root_mem_cgroup->css.cgroup);
+       cgroup_rstat_flush_atomic(root_mem_cgroup->css.cgroup);
        atomic_set(&stats_flush_threshold, 0);
        spin_unlock_irqrestore(&stats_flush_lock, flag);
 }