From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shakeel Butt Subject: [PATCH 1/3] mm: page_counter: remove unneeded atomic ops for low/min Date: Mon, 22 Aug 2022 00:17:35 +0000 Message-ID: <20220822001737.4120417-2-shakeelb@google.com> References: <20220822001737.4120417-1-shakeelb@google.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:references:mime-version:message-id:in-reply-to :date:from:to:cc; bh=PKFRaxD4qQqEIFqu3chPSEEEaimoA7SPNFa30ZMS/uU=; b=HizZvrBQiCe/lTGkboVezrNH98vpHv6pPqN3AxEJH/hFrU99YqU4n2tDb7vx0BDvjD bQrrXzlJxZNS5VEi+6ur1985jYp1mqaVxFam9zQg29fgy4j8FDwrvk2EWIEw9zZcLyy8 ZrbSnLWlxJzAlcK4inCb0YBuOPVU8Pf6wgn3U0AS+YKBi3N8fLf+SDkLifHnsuVpXtE9 VW+MgYxWYsl4FT5vPrWtjoQKUyoGIDwGhmbfEnhOfVukKNjsvqjWPYthJA+lrTU4JyRJ Sj3VMg2YYPUcwhLJDwgqi0QQBI7r5yYyU5d+lRAwuifJcVjqGV647qwS/PzhpquTv4FZ z7vQ== In-Reply-To: <20220822001737.4120417-1-shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song Cc: =?UTF-8?q?Michal=20Koutn=C3=BD?= , Eric Dumazet , Soheil Hassas Yeganeh , Feng Tang , Oliver Sang , Andrew Morton , lkp-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Shakeel Butt For cgroups using low or min protections, the function propagate_protected_usage() was doing an atomic xchg() operation irrespectively. It only needs to do that operation if the new value of protection is different from older one. This patch does that. To evaluate the impact of this optimization, on a 72 CPUs machine, we ran the following workload in a three level of cgroup hierarchy with top level having min and low setup appropriately. More specifically memory.min equal to size of netperf binary and memory.low double of that. $ netserver -6 # 36 instances of netperf with following params $ netperf -6 -H ::1 -l 60 -t TCP_SENDFILE -- -m 10K Results (average throughput of netperf): Without (6.0-rc1) 10482.7 Mbps With patch 14542.5 Mbps (38.7% improvement) With the patch, the throughput improved by 38.7% Signed-off-by: Shakeel Butt Reported-by: kernel test robot --- mm/page_counter.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/mm/page_counter.c b/mm/page_counter.c index eb156ff5d603..47711aa28161 100644 --- a/mm/page_counter.c +++ b/mm/page_counter.c @@ -17,24 +17,23 @@ static void propagate_protected_usage(struct page_counter *c, unsigned long usage) { unsigned long protected, old_protected; - unsigned long low, min; long delta; if (!c->parent) return; - min = READ_ONCE(c->min); - if (min || atomic_long_read(&c->min_usage)) { - protected = min(usage, min); + protected = min(usage, READ_ONCE(c->min)); + old_protected = atomic_long_read(&c->min_usage); + if (protected != old_protected) { old_protected = atomic_long_xchg(&c->min_usage, protected); delta = protected - old_protected; if (delta) atomic_long_add(delta, &c->parent->children_min_usage); } - low = READ_ONCE(c->low); - if (low || atomic_long_read(&c->low_usage)) { - protected = min(usage, low); + protected = min(usage, READ_ONCE(c->low)); + old_protected = atomic_long_read(&c->low_usage); + if (protected != old_protected) { old_protected = atomic_long_xchg(&c->low_usage, protected); delta = protected - old_protected; if (delta) -- 2.37.1.595.g718a3a8f04-goog