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dkim=pass header.d=google.com header.s=20210112 header.b=guVICWeq; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf22.hostedemail.com: domain of soheil@google.com designates 209.85.208.44 as permitted sender) smtp.mailfrom=soheil@google.com X-Rspamd-Server: rspam04 X-Stat-Signature: eobeakun5omn9i3447p68bq3jk5mpwbr X-HE-Tag: 1661127652-255254 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Aug 21, 2022 at 8:17 PM Shakeel Butt wrote: > > 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 Nice speed up! Acked-by: Soheil Hassas Yeganeh > --- > 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 >