From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f72.google.com (mail-it0-f72.google.com [209.85.214.72]) by kanga.kvack.org (Postfix) with ESMTP id B92A96B0038 for ; Fri, 17 Nov 2017 11:20:42 -0500 (EST) Received: by mail-it0-f72.google.com with SMTP id x28so3632433ita.9 for ; Fri, 17 Nov 2017 08:20:42 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id o11sor3063768ito.73.2017.11.17.08.20.41 for (Google Transport Security); Fri, 17 Nov 2017 08:20:41 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20171117155509.GA920@castle> References: <1510888199-5886-1-git-send-email-laoar.shao@gmail.com> <20171117155509.GA920@castle> From: Yafang Shao Date: Sat, 18 Nov 2017 00:20:40 +0800 Message-ID: Subject: Re: [PATCH] mm/shmem: set default tmpfs size according to memcg limit Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Roman Gushchin Cc: Shakeel Butt , Andrew Morton , Johannes Weiner , Vladimir Davydov , Michal Hocko , Tejun Heo , khlebnikov@yandex-team.ru, mka@chromium.org, Hugh Dickins , Cgroups , Linux MM , LKML 2017-11-17 23:55 GMT+08:00 Roman Gushchin : > On Thu, Nov 16, 2017 at 08:43:17PM -0800, Shakeel Butt wrote: >> On Thu, Nov 16, 2017 at 7:09 PM, Yafang Shao wrote: >> > Currently the default tmpfs size is totalram_pages / 2 if mount tmpfs >> > without "-o size=XXX". >> > When we mount tmpfs in a container(i.e. docker), it is also >> > totalram_pages / 2 regardless of the memory limit on this container. >> > That may easily cause OOM if tmpfs occupied too much memory when swap is >> > off. >> > So when we mount tmpfs in a memcg, the default size should be limited by >> > the memcg memory.limit. >> > >> >> The pages of the tmpfs files are charged to the memcg of allocators >> which can be in memcg different from the memcg in which the mount >> operation happened. So, tying the size of a tmpfs mount where it was >> mounted does not make much sense. > > Also, memory limit is adjustable, Yes. But that's irrelevant. > and using a particular limit value > at a moment of tmpfs mounting doesn't provide any warranties further. > I can not agree. The default size of tmpfs is totalram / 2, the reason we do this is to provide any warranties further IMHO. > Is there a reason why the userspace app which is mounting tmpfs can't > set the size based on memory.limit? That's because of misuse. The application should set size with "-o size=" when mount tmpfs, but not all applications do this. As we can't guarantee that all applications will do this, we should give them a proper default value. Thanks Yafang -- 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