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([2804:1b3:a800:6912:c477:c73a:cf7c:3a27]) by smtp.gmail.com with ESMTPSA id g20-20020a9d6b14000000b0068848d6b231sm1480090otp.30.2023.01.27.00.12.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Jan 2023 00:12:18 -0800 (PST) Message-ID: <601fc35a8cc2167e53e45c636fccb2d899fd7c50.camel@redhat.com> Subject: Re: [PATCH v2 0/5] Introduce memcg_stock_pcp remote draining From: Leonardo =?ISO-8859-1?Q?Br=E1s?= To: Michal Hocko , Roman Gushchin Cc: 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 Date: Fri, 27 Jan 2023 05:12:13 -0300 In-Reply-To: <52a0f1e593b1ec0ca7e417ba37680d65df22de82.camel@redhat.com> References: <20230125073502.743446-1-leobras@redhat.com> <9e61ab53e1419a144f774b95230b789244895424.camel@redhat.com> <52a0f1e593b1ec0ca7e417ba37680d65df22de82.camel@redhat.com> User-Agent: Evolution 3.46.2 MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 2392080017 X-Rspamd-Server: rspam01 X-Stat-Signature: kcxijrmk1s5d1qsbexoj7hm8wh3fz5n9 X-HE-Tag: 1674807141-105323 X-HE-Meta: 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 WmqX3jX2 AELen4VvmNDHL2Ghn0+IayGo/4MHRVPRqLd847HvajOEn5TrRxSmIREqBu1OxhsoWOvf0NMDwZ+3/nV1yUyxdrLG6gaWUXUAS+f8rrQ6JnoBErxV/9AVfo/ueOPNQilGDMSx1uFcJjfqp/PrnyC/aOJQfDTsBYoNKuA7L7ERj31SZyOchLuYBQ2BfHAyRxuWq3z4WSS/dE9iuz+sMiBq9S/bNrnkWYteGS7CqoUANT5la7kPPH9T42iVHud6aQwomuI9iISnp9KxHLPfqBnrQko0b2LJqEFAvRPthBFXvQi16xqBtBCfnGq3V+5r60SDosJNNfHnu7L7oV3DNWArQijRCDTkXJu09euN9CyxTwu/CV6V4C47C7aHR47rAE3uBUBGIqCFZhqRNCbhcuuqdjAYRcO73nTpHwK73ZKwqeH9Nh56Bt5FBPzfaN+d8EiVpmMH2HkTguDuU1KepC4hMzqY+ig2IGZ9Ngu2NlINf+UkduCk= 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, 2023-01-27 at 04:22 -0300, Leonardo Br=C3=A1s wrote: > On Fri, 2023-01-27 at 08:11 +0100, Michal Hocko wrote: > > [Cc Frederic] > >=20 > > 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 q= uota > > > > > and move it locally. I wonder in such circumstances if we need to= disable the pcp-caching > > > > > on per-cgroup basis. > > > >=20 > > > > I think it would be more than sufficient to disable pcp charging on= an > > > > isolated cpu. > > >=20 > > > It might have significant performance consequences. > >=20 > > Is it really significant? > >=20 > > > I'd rather opt out of stock draining for isolated cpus: it might slig= htly reduce > > > the accuracy of memory limits and slightly increase the memory footpr= int (all > > > those dying memcgs...), but the impact will be limited. Actually it i= s limited > > > by the number of cpus. > >=20 > > Hmm, OK, I have misunderstood your proposal. Yes, the overal pcp charge= s > > 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). > >=20 > > My first thought was that those charges could be left behind without an= y > > 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. > >=20 > > So yes, this is actually a better and even simpler solution. All we nee= d > > 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 *ro= ot_memcg) > > =09=09struct mem_cgroup *memcg; > > =09=09bool flush =3D false; > > =20 > > +=09=09if (cpu_is_isolated(cpu)) > > +=09=09=09continue; > > + > > =09=09rcu_read_lock(); > > =09=09memcg =3D stock->cached; > > =09=09if (memcg && stock->nr_pages && > >=20 > > 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? >=20 >=20 > IIUC, 'if (cpu_is_isolated())' would be instead: >=20 > 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)) Not sure why I added smp_processor_id() instead of cpu. I think I need some sleep. :)