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mx.microsoft.com 1; spf=pass smtp.mailfrom=intel.com; dmarc=pass action=none header.from=intel.com; dkim=pass header.d=intel.com; arc=none Received: from MN0PR11MB6304.namprd11.prod.outlook.com (2603:10b6:208:3c0::7) by CY4PR11MB1398.namprd11.prod.outlook.com (2603:10b6:903:2a::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5546.16; Mon, 22 Aug 2022 02:39:44 +0000 Received: from MN0PR11MB6304.namprd11.prod.outlook.com ([fe80::d446:1cb8:3071:f4e8]) by MN0PR11MB6304.namprd11.prod.outlook.com ([fe80::d446:1cb8:3071:f4e8%6]) with mapi id 15.20.5546.022; Mon, 22 Aug 2022 02:39:44 +0000 Date: Mon, 22 Aug 2022 10:39:02 +0800 From: Feng Tang To: Shakeel Butt CC: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Michal Koutn?? , Eric Dumazet , Soheil Hassas Yeganeh , "Sang, Oliver" , Andrew Morton , "lkp@lists.01.org" , "cgroups@vger.kernel.org" , "linux-mm@kvack.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/3] mm: page_counter: remove unneeded atomic ops for low/min Message-ID: References: <20220822001737.4120417-1-shakeelb@google.com> <20220822001737.4120417-2-shakeelb@google.com> Content-Type: text/plain; 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bh=2/L2pj0oVIZeUCUZg+p09BvICWmsvmKpZ2XB8VfNgdw=; b=4jHH8HrSljNZZAtU+Sdq/MHE/hEttQkIVAWR6UO/jbDN04CTCVGGRaRt3+++vQY+r+ysLp DIOlFRZcjBdswHSUfjmmSgyEP/54PvEW5vm0AZ1hMuFx9fr3R9kCKqQTzRGk6Okl0j5/wh ZiIPTPCK4Fm6yvbgBJ7inBqD4xQxnhQ= X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: C3C9A140083 X-Rspam-User: X-Stat-Signature: eusa99bxp7s5t57ejj4e4w1eh3813wt7 Authentication-Results: imf09.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=iGgVfG8S; spf=pass (imf09.hostedemail.com: domain of feng.tang@intel.com designates 134.134.136.24 as permitted sender) smtp.mailfrom=feng.tang@intel.com; arc=reject ("signature check failed: fail, {[1] = sig:microsoft.com:reject}"); dmarc=pass (policy=none) header.from=intel.com X-HE-Tag: 1661135995-417709 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 Mon, Aug 22, 2022 at 08:17:35AM +0800, 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 Reviewed-by: Feng Tang Thanks! - Feng > --- > 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 >