lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20230921081057.3440885-2-yosryahmed@google.com>
Date:   Thu, 21 Sep 2023 08:10:53 +0000
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Ivan Babrou <ivan@...udflare.com>, Tejun Heo <tj@...nel.org>,
        "Michal Koutný" <mkoutny@...e.com>,
        Waiman Long <longman@...hat.com>, kernel-team@...udflare.com,
        Wei Xu <weixugc@...gle.com>, Greg Thelen <gthelen@...gle.com>,
        linux-mm@...ck.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, Yosry Ahmed <yosryahmed@...gle.com>
Subject: [PATCH 1/5] mm: memcg: change flush_next_time to flush_last_time

flush_next_time is an inaccurate name. It's not the next time that
periodic flushing will happen, it's rather the next time that
ratelimited flushing can happen if the periodic flusher is late.

Simplify its semantics by just storing the timestamp of the last flush
instead, flush_last_time. Move the 2*FLUSH_TIME addition to
mem_cgroup_flush_stats_ratelimited(), and add a comment explaining it.
This way, all the ratelimiting semantics live in one place.

No functional change intended.

Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
---
 mm/memcontrol.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 927c64d3cbcb..49562dfdeab2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -590,7 +590,7 @@ static DECLARE_DEFERRABLE_WORK(stats_flush_dwork, flush_memcg_stats_dwork);
 static DEFINE_PER_CPU(unsigned int, stats_updates);
 static atomic_t stats_flush_ongoing = ATOMIC_INIT(0);
 static atomic_t stats_flush_threshold = ATOMIC_INIT(0);
-static u64 flush_next_time;
+static u64 flush_last_time;
 
 #define FLUSH_TIME (2UL*HZ)
 
@@ -650,7 +650,7 @@ static void do_flush_stats(void)
 	    atomic_xchg(&stats_flush_ongoing, 1))
 		return;
 
-	WRITE_ONCE(flush_next_time, jiffies_64 + 2*FLUSH_TIME);
+	WRITE_ONCE(flush_last_time, jiffies_64);
 
 	cgroup_rstat_flush(root_mem_cgroup->css.cgroup);
 
@@ -666,7 +666,8 @@ void mem_cgroup_flush_stats(void)
 
 void mem_cgroup_flush_stats_ratelimited(void)
 {
-	if (time_after64(jiffies_64, READ_ONCE(flush_next_time)))
+	/* Only flush if the periodic flusher is one full cycle late */
+	if (time_after64(jiffies_64, READ_ONCE(flush_last_time) + 2*FLUSH_TIME))
 		mem_cgroup_flush_stats();
 }
 
-- 
2.42.0.459.ge4e396fd5e-goog

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ