From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 76F826B0005 for ; Thu, 31 May 2018 04:23:25 -0400 (EDT) Received: by mail-pg0-f71.google.com with SMTP id v133-v6so6029307pgb.10 for ; Thu, 31 May 2018 01:23:25 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id 14-v6sor13205613pfp.13.2018.05.31.01.23.23 for (Google Transport Security); Thu, 31 May 2018 01:23:23 -0700 (PDT) Date: Thu, 31 May 2018 17:23:17 +0900 From: Minchan Kim Subject: Re: [PATCH] memcg: force charge kmem counter too Message-ID: <20180531082317.GA52285@rodete-desktop-imager.corp.google.com> References: <20180525185501.82098-1-shakeelb@google.com> <20180526185144.xvh7ejlyelzvqwdb@esperanza> <20180528091110.GG1517@dhcp22.suse.cz> <20180529083153.GR27180@dhcp22.suse.cz> <20180531060133.GA31477@rodete-desktop-imager.corp.google.com> <20180531065642.GI15278@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180531065642.GI15278@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Shakeel Butt , Vladimir Davydov , Andrew Morton , Greg Thelen , Johannes Weiner , Linux MM , Cgroups , LKML On Thu, May 31, 2018 at 08:56:42AM +0200, Michal Hocko wrote: > On Thu 31-05-18 15:01:33, Minchan Kim wrote: > > On Wed, May 30, 2018 at 11:14:33AM -0700, Shakeel Butt wrote: > > > On Tue, May 29, 2018 at 1:31 AM, Michal Hocko wrote: > > > > On Mon 28-05-18 10:23:07, Shakeel Butt wrote: > > > >> On Mon, May 28, 2018 at 2:11 AM, Michal Hocko wrote: > > > >> Though is there a precedence where the broken feature is not fixed > > > >> because an alternative is available? > > > > > > > > Well, I can see how breaking GFP_NOFAIL semantic is problematic, on the > > > > other hand we keep saying that kmem accounting in v1 is hard usable and > > > > strongly discourage people from using it. Sure we can add the code which > > > > handles _this_ particular case but that wouldn't make the whole thing > > > > more usable I strongly suspect. Maybe I am wrong and you can provide > > > > some specific examples. Is GFP_NOFAIL that common to matter? > > > > > > > > In any case we should balance between the code maintainability here. > > > > Adding more cruft into the allocator path is not free. > > > > > > > > > > We do not use kmem limits internally and this is something I found > > > through code inspection. If this patch is increasing the cost of code > > > maintainability I am fine with dropping it but at least there should a > > > comment saying that kmem limits are broken and no need fix. > > > > I agree. > > > > Even, I didn't know kmem is strongly discouraged until now. Then, > > why is it enabled by default on cgroup v1? > > You have to set a non-zero limit to make it active IIRC. The code is Maybe, no. I didn't set anything. IOW, it was a default without any setting and I hit this as you can remember. http://lkml.kernel.org/r/<20180418022912.248417-1-minchan@kernel.org> We don't need to allocate memory for stuff even maintainers discourage. > compiled in because v2 enables it by default. > > > Let's turn if off with comment "It's broken so do not use/fix. Instead, > > please move to cgroup v2". > > -- > Michal Hocko > SUSE Labs