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Thu, 20 Feb 2020 12:54:17 -0800 (PST) Received: from localhost ([2620:10d:c091:500::55b1]) by smtp.gmail.com with ESMTPSA id g9sm420153qkl.11.2020.02.20.12.54.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Feb 2020 12:54:17 -0800 (PST) Date: Thu, 20 Feb 2020 15:54:16 -0500 From: Tejun Heo To: Daniel Jordan Cc: Johannes Weiner , Michal Hocko , Andrew Morton , Roman Gushchin , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Peter Zijlstra Subject: Re: [PATCH] mm: memcontrol: asynchronous reclaim for memory.high Message-ID: <20200220205416.GI698990@mtj.thefacebook.com> References: <20200219183731.GC11847@dhcp22.suse.cz> <20200219191618.GB54486@cmpxchg.org> <20200219195332.GE11847@dhcp22.suse.cz> <20200219214112.4kt573kyzbvmbvn3@ca-dmjordan1.us.oracle.com> <20200219220859.GF54486@cmpxchg.org> <20200220154524.dql3i5brnjjwecft@ca-dmjordan1.us.oracle.com> <20200220155651.GG698990@mtj.thefacebook.com> <20200220182326.ubcjycaubgykiy6e@ca-dmjordan1.us.oracle.com> <20200220184545.GH698990@mtj.thefacebook.com> <20200220195535.7xblt45akld6eftj@ca-dmjordan1.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200220195535.7xblt45akld6eftj@ca-dmjordan1.us.oracle.com> 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: Hello, Daniel. On Thu, Feb 20, 2020 at 02:55:35PM -0500, Daniel Jordan wrote: > On Thu, Feb 20, 2020 at 01:45:45PM -0500, Tejun Heo wrote: > > The setup cost can be lazy optimized but it'd still have to bounce the > > tiny pieces of work to different threads instead of processing them in > > one fell swoop from the same context, which most likely is gonna be > > untenably expensive. > > I see, your last mail is clearer now. If it's easy to do, a pointer to where > this happens would help so we're on the same page. Network packet rx is the clearest example I think, but you already mentioned it. Reclaim is less so but when kswapd reclaims, it walks everybody, and there can be a lot of small cgroups. Thanks. -- tejun