From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Weiner Subject: Re: [PATCH 1/2] mm, memcg: reset memory.low during memcg offlining Date: Thu, 27 Jul 2017 10:35:21 -0400 Message-ID: <20170727143521.GB19738@cmpxchg.org> References: <20170726083017.3yzeucmi7lcj46qd@esperanza> <20170727130428.28856-1-guro@fb.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=cmpxchg.org ; s=x; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject: Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=HoYyAnb++ZhQajX5TSWqPNhSuHLUPN3orPo161uOhUs=; b=ubaFF7npQySO4B3maN+plZlCce YntzlwbGwkB19lkVMZFpMKSRug1HSVLs3Y4W4FC0aAO6ZznonomT3jDDdArMPukRooQcI6881jv7b tNnTbyukExeKZfsF7dEZDP4hxtKIX3gecJEPFgE+m+x2Yiej+VGzgI+7i6/NFGmPvq18=; Content-Disposition: inline In-Reply-To: <20170727130428.28856-1-guro@fb.com> Sender: linux-kernel-owner@vger.kernel.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 , Tejun Heo , Michal Hocko , kernel-team@fb.com, cgroups@vger.kernel.org, linux-mm@kvack.org, Andrew Morton CC Andrew - can you route these through the -mm tree please? On Thu, Jul 27, 2017 at 02:04:27PM +0100, Roman Gushchin wrote: > A removed memory cgroup with a defined memory.low and some belonging > pagecache has very low chances to be freed. > > If a cgroup has been removed, there is likely no memory pressure inside > the cgroup, and the pagecache is protected from the external pressure > by the defined low limit. The cgroup will be freed only after > the reclaim of all belonging pages. And it will not happen until > there are any reclaimable memory in the system. That means, > there is a good chance, that a cold pagecache will reside > in the memory for an undefined amount of time, wasting > system resources. > > This problem was fixed earlier by commit fa06235b8eb0 > ("cgroup: reset css on destruction"), but it's not a best way > to do it, as we can't really reset all limits/counters during > cgroup offlining. > > 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: Johannes Weiner