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bh=2xvZjQHSmlkJ++xydcKZz/+IOLXbzOFKz6MRvf+IGoQ=; b=QYrMxh5iF8tEZkkIFQiaE0AmzYlUt1+vYWDsddn9lZSskr2jXsldh5NvFZbS6xqZHH9a8d uZwo40l3QwPpd4O9Ws+Lgz2Ss0yY/Rd4JXSO7AA1yqFZGpnGEFRWK8pc9UK4jbMEbt8qmu hNG0Yiin9IUP1Enty4F5i+/fAEiPJ2Y= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 6B6A61336F; Fri, 27 Jan 2023 09:23:29 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id fPn1FxGY02PDGQAAMHmgww (envelope-from ); Fri, 27 Jan 2023 09:23:29 +0000 Date: Fri, 27 Jan 2023 10:23:28 +0100 From: Michal Hocko To: Leonardo =?iso-8859-1?Q?Br=E1s?= Cc: Roman Gushchin , Marcelo Tosatti , Johannes Weiner , Shakeel Butt , Muchun Song , Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Frederic Weisbecker Subject: Re: [PATCH v2 0/5] Introduce memcg_stock_pcp remote draining Message-ID: References: <20230125073502.743446-1-leobras@redhat.com> <9e61ab53e1419a144f774b95230b789244895424.camel@redhat.com> <52a0f1e593b1ec0ca7e417ba37680d65df22de82.camel@redhat.com> <601fc35a8cc2167e53e45c636fccb2d899fd7c50.camel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <601fc35a8cc2167e53e45c636fccb2d899fd7c50.camel@redhat.com> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 2022F180015 X-Rspam-User: X-Stat-Signature: ddm5ribwpijdrp19nkmk8gmzzzjsm3eb X-HE-Tag: 1674811410-798694 X-HE-Meta: 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 BLtZvYnF hv+N2G0KKaHi/m8NKo9kBrjIqGhSt97UQDWb5jPuGDxKyT0aWhM/Z0ColHTUehOjr3u6OY4YDMyp2aOyx4a/a6QQQb8k0e0lIjGIMva2yinUL9ck98Pr8ZFuQx+Gy+Z9rHitUxxhQD3TNgFRuP99kAJVR/kWHM/Oofrw0LJlK+7m0Sifyt/IAg+0SfgFb/uBi3mya3IUJAQZdWSEkwZd9oleRqVADTHEUb7Ga0I5H0XKIi7q2JXQHo+lLY9xnynAmyY40 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 Fri 27-01-23 05:12:13, Leonardo Brás wrote: > On Fri, 2023-01-27 at 04:22 -0300, Leonardo Brás wrote: > > On Fri, 2023-01-27 at 08:11 +0100, Michal Hocko wrote: > > > [Cc Frederic] > > > > > > On Thu 26-01-23 15:12:35, Roman Gushchin wrote: > > > > On Thu, Jan 26, 2023 at 08:41:34AM +0100, Michal Hocko wrote: > > > [...] > > > > > > Essentially each cpu will try to grab the remains of the memory quota > > > > > > and move it locally. I wonder in such circumstances if we need to disable the pcp-caching > > > > > > on per-cgroup basis. > > > > > > > > > > I think it would be more than sufficient to disable pcp charging on an > > > > > isolated cpu. > > > > > > > > It might have significant performance consequences. > > > > > > Is it really significant? > > > > > > > I'd rather opt out of stock draining for isolated cpus: it might slightly reduce > > > > the accuracy of memory limits and slightly increase the memory footprint (all > > > > those dying memcgs...), but the impact will be limited. Actually it is limited > > > > by the number of cpus. > > > > > > Hmm, OK, I have misunderstood your proposal. Yes, the overal pcp charges > > > potentially left behind should be small and that shouldn't really be a > > > concern for memcg oom situations (unless the limit is very small and > > > workloads on isolated cpus using small hard limits is way beyond my > > > imagination). > > > > > > My first thought was that those charges could be left behind without any > > > upper bound but in reality sooner or later something should be running > > > on those cpus and if the memcg is gone the pcp cache would get refilled > > > and old charges gone. > > > > > > So yes, this is actually a better and even simpler solution. All we need > > > is something like this > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > > index ab457f0394ab..13b84bbd70ba 100644 > > > --- a/mm/memcontrol.c > > > +++ b/mm/memcontrol.c > > > @@ -2344,6 +2344,9 @@ static void drain_all_stock(struct mem_cgroup *root_memcg) > > > struct mem_cgroup *memcg; > > > bool flush = false; > > > > > > + if (cpu_is_isolated(cpu)) > > > + continue; > > > + > > > rcu_read_lock(); > > > memcg = stock->cached; > > > if (memcg && stock->nr_pages && > > > > > > There is no such cpu_is_isolated() AFAICS so we would need a help from > > > NOHZ and cpuisol people to create one for us. Frederic, would such an > > > abstraction make any sense from your POV? > > > > > > IIUC, 'if (cpu_is_isolated())' would be instead: > > > > if (!housekeeping_cpu(smp_processor_id(), HK_TYPE_DOMAIN) || > > !housekeeping_cpu(smp_processor_id(), HK_TYPE_WQ) > > oh, sorry 's/smp_processor_id()/cpu/' here: > > if(!housekeeping_cpu(cpu, HK_TYPE_DOMAIN) || !housekeeping_cpu(cpu, HK_TYPE_WQ)) Or maybe we can get a nice abstract API so that we do not have to really care about those low level details. I do not really know what those really mean and hopefully I shouldn't really need to know. -- Michal Hocko SUSE Labs