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t=1674824642; bh=5/c2AB+sVfBr3bN7TBwjNlpfu3p70/0YG6h0yWH9Mpg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UHJpxk7EFq6ak/R8ldY7KoUAXIlE2dZyXktge26XKHv9g66w8Izx9NuNibJZEOrwz HxgvWvRBRErjHhikZlfyKKCHqBxbFM3JYu6q2pUincrQeHyB5ye561Ic/ed1NnY5wC znydMQCtv2iEuj6odOpLLra+NAdugUihIlaD7nwrbZnuZI8L9JMr2az2IqhC5Lsy+h y45Gis+7DoDk/XNeosPI979PPqlzsCRl6GF73eF9/yUAZxdtDwFVVvgxEQudOUhGH7 ZY1rOejeZI0pqRMK2/Wk+85B4AZ/IhS29y6GRuxXlaDIuQ5CWk6Zg/qxpmyau11j8o rSLXu+bX8FWaw== Date: Fri, 27 Jan 2023 14:03:59 +0100 From: Frederic Weisbecker To: Leonardo =?iso-8859-1?Q?Br=E1s?= Cc: Michal Hocko , 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-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 82A9440029 X-Stat-Signature: xpoh7ytes1pfcquso6c1f6fma99oagxp X-HE-Tag: 1674824645-386968 X-HE-Meta: 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 7S4YZu89 0S8VV237NskRoyQ4rjmegmExZweFnQ36qZk8wuwagxK44lZS74HXX35DT4CaLzJ/SZd9KhwGx5Na+Lv6eNSGAPV7bKHBIYiaBITGaZ3LSsLI+CDOX3I9OH6pghxiQOhX1WNmqNsdYaHc5oiORoOB9TD9retHxrecLXzy4ICa3rO2JuW7o1JNCPv6qUVFFzRwz8XMx6TRHgPnJAozlncntQB6rtJprdxWhU1upqsrDSNybthvpA1+3nvpD/pT3IeCB7xZYfwOczTjztILFw6py0y6SqK8yS4n7b3uu+qbjpU3SCnJz8oZMPj9pE+PxYInAy0EOS4coGQSyQatbuj1nNHgU9HjJv/6Dm5jaOQFfAYx4+uZw3TNbwnGc2FHwKrewGjB1ezdfWRMPlLo= 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, Jan 27, 2023 at 05:12:13AM -0300, Leonardo Brás wrote: > On Fri, 2023-01-27 at 04:22 -0300, Leonardo Brás wrote: > > > 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)) Do you also need to handle cpuset.sched_load_balance=0 (aka. cpuset v2 "isolated" partition type). It has the same effect as isolcpus=, but it can be changed at runtime. And then on_null_domain() look like what you need. You'd have to make that API more generally available though, and rename it to something like "bool cpu_has_null_domain(int cpu)". But then you also need to handle concurrent cpuset changes. If you can tolerate it to be racy, then RCU alone is fine. Thanks.