From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 2/2] cgroup: revert fa06235b8eb0 ("cgroup: reset css on destruction") Date: Thu, 27 Jul 2017 09:52:40 -0400 Message-ID: <20170727135240.GE742618@devbig577.frc2.facebook.com> References: <20170726083017.3yzeucmi7lcj46qd@esperanza> <20170727130428.28856-1-guro@fb.com> <20170727130428.28856-2-guro@fb.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=tduT3S5mtmsNf9tFYhFQC9Nt3OHd4w+sTKoPRR7DQsg=; b=O0xBq4ij2EU8fKnY4+AxM8zaqh5j1d86IHgYtkbFC9fSKE0Qvtd7QiVUhL6x+s+3Rr KCef+sR/Lzqxm45gzocD6pRLizee1mnzUYr6dWVO8R6uZzhYyxG5p5e7hmcUcrnloMbR Qt/HdaRcCLxHla22ga7+2t6Rsu50P++Q+CWEzP6acKm4vg1BpEL/xvfGZmE00UYtQR+R 4ZsmaLkWOcJboFH7TbHtODQhEZYLWQXcbl2s7DdBv48q2CkBP3hJ9Z6KveDkcm6/PECg Jq8hxbLQ1hsCsDrp9mC1RFCSFZoCEih/zEKEsnBMD0moBgaguRdYAfp9ri4TxvrArM6x GyjQ== Content-Disposition: inline In-Reply-To: <20170727130428.28856-2-guro@fb.com> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Roman Gushchin Cc: linux-kernel@vger.kernel.org, Vladimir Davydov , Johannes Weiner , Michal Hocko , kernel-team@fb.com, cgroups@vger.kernel.org, linux-mm@kvack.org On Thu, Jul 27, 2017 at 02:04:28PM +0100, Roman Gushchin wrote: > Commit fa06235b8eb0 ("cgroup: reset css on destruction") caused > css_reset callback to be called from the offlining path. Although > it solves the problem mentioned in the commit description > ("For instance, memory cgroup needs to reset memory.low, otherwise > pages charged to a dead cgroup might never get reclaimed."), > generally speaking, it's not correct. > > An offline cgroup can still be a resource domain, and we shouldn't > grant it more resources than it had before deletion. > > For instance, if an offline memory cgroup has dirty pages, we should > still imply i/o limits during writeback. > > The css_reset callback is designed to return the cgroup state > into the original state, that means reset all limits and counters. > It's spomething different from the offlining, and we shouldn't use > it from the offlining path. Instead, we should adjust necessary > settings from the per-controller css_offline callbacks (e.g. reset > memory.low). > > Signed-off-by: Roman Gushchin > Cc: Vladimir Davydov > Cc: Tejun Heo > Cc: Johannes Weiner > Cc: Michal Hocko > Cc: kernel-team@fb.com > Cc: cgroups@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org Acked-by: Tejun Heo Please feel free to route with the previous patch through -mm. Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org