From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9289CC433EF for ; Wed, 20 Apr 2022 12:47:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353832AbiDTMuA (ORCPT ); Wed, 20 Apr 2022 08:50:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348748AbiDTMt7 (ORCPT ); Wed, 20 Apr 2022 08:49:59 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA72B3C73F; Wed, 20 Apr 2022 05:47:13 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 0A1F1210F1; Wed, 20 Apr 2022 12:47:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1650458832; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=fE2JVFjVSECX2xSom7dha9uadrw2m4rx6MxVgcht3TU=; b=ls08cpYNS6BsFKbzep+CNbq8sfVdl2ellBWBujxnccydNYGlZusiruxwRBWAGNdG+LbEjN jBIdNmHiFta1RBcAXwfZU0dmIdTZsOgoaKPo4njd2eiadAdPKoabYOFObP16BYeeo/IWJ6 6qVYRksrngynbRG+maQ3Tkc4EqFNkn0= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 261B62C142; Wed, 20 Apr 2022 12:47:11 +0000 (UTC) Date: Wed, 20 Apr 2022 14:47:10 +0200 From: Michal Hocko To: Yosry Ahmed Cc: Johannes Weiner , Shakeel Butt , Andrew Morton , Roman Gushchin , David Rientjes , Tejun Heo , Dan Schatzberg , Zefan Li , Jonathan Corbet , Shuah Khan , Yu Zhao , Dave Hansen , Wei Xu , Greg Thelen , Chen Wandun , Vaibhav Jain , Michal =?iso-8859-1?Q?Koutn=FD?= , Tim Chen , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, Linux Kernel Mailing List , Linux-MM , linux-kselftest@vger.kernel.org Subject: Re: [PATCH v3 1/4] memcg: introduce per-memcg reclaim interface Message-ID: References: <20220408045743.1432968-1-yosryahmed@google.com> <20220408045743.1432968-2-yosryahmed@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Thu 14-04-22 10:25:29, Yosry Ahmed wrote: > On Fri, Apr 8, 2022 at 1:08 PM Yosry Ahmed wrote: > > > > On Fri, Apr 8, 2022 at 7:55 AM Dan Schatzberg wrote: > > > > > > On Fri, Apr 08, 2022 at 04:11:05PM +0200, Michal Hocko wrote: > > > > Regarding "max" as a possible input. I am not really sure to be honest. > > > > I can imagine that it could be legit to simply reclaim all the charges > > > > (e.g. before removing the memcg) which should be achieveable by > > > > reclaiming the reported consumption. Or what exactly should be the > > > > semantic? > > > > > > Yeah, it just allows you to avoid reading memory.current to just > > > reclaim everything if you can specify "max" - you're still protected > > > by nretries to eventually bail out. Mostly, though I just feel like > > > supporting "max" makes memory.reclaim semetric with a lot of the > > > cgroup memory control files which tend to support "max". > > > > One possible approach here is to have force_empty behavior when we > > write "max" to memory.reclaim. From Google's perspective we don't have > > a preference, but it seems to me like logical behavior. We can do this > > either by directly calling mem_cgroup_force_empty() or just draining > > stock and lrus in memory_reclaim(). > > > > This actually brings up another interesting point. Do you think we > > should drain lrus if try_to_free_mem_cgroup_pages() fails to reclaim > > the request amount? We can do this after the first call or before the > > last one. It could introduce more evictable pages for > > try_to_free_mem_cgroup_pages() to free. > > Hey Michal, any thoughts on this? I am looking for feedback on this > before I send out v4. As I've already said I do not have strong preferences for the "max" value to be accepted by the interface. Maybe you can add a support for max in a separate patch so the discussion would not delay the rest of the work. For the LRU draining I do not see any problem for that to be added. The overhead of the operation would increase, especially on larger machines, which could be a concern. So the real question is whether not doing so is a big problem. Our force_empty implementation optimistically drains pcp caches but please note that this is not really guranteeing anything as charges can happen at any time. -- Michal Hocko SUSE Labs