From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id EB091828E1 for ; Wed, 29 Jun 2016 16:14:12 -0400 (EDT) Received: by mail-qk0-f198.google.com with SMTP id e3so26332518qkd.2 for ; Wed, 29 Jun 2016 13:14:12 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id j1si1226qkf.317.2016.06.29.13.14.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 Jun 2016 13:14:12 -0700 (PDT) Date: Wed, 29 Jun 2016 22:14:09 +0200 From: Oleg Nesterov Subject: Re: [PATCH] mm,oom: use per signal_struct flag rather than clear TIF_MEMDIE Message-ID: <20160629201409.GB19253@redhat.com> References: <1466766121-8164-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20160624215627.GA1148@redhat.com> <201606251444.EGJ69787.FtMOFJOLSHFQOV@I-love.SAKURA.ne.jp> <20160627092326.GD31799@dhcp22.suse.cz> <20160627103609.GE31799@dhcp22.suse.cz> <20160627155119.GA17686@redhat.com> <20160627160616.GN31799@dhcp22.suse.cz> <20160627175555.GA24370@redhat.com> <20160628101956.GA510@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160628101956.GA510@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Tetsuo Handa , linux-mm@kvack.org, vdavydov@virtuozzo.com, rientjes@google.com On 06/28, Michal Hocko wrote: > > On Mon 27-06-16 19:55:55, Oleg Nesterov wrote: > > On 06/27, Michal Hocko wrote: > > > > > > On Mon 27-06-16 17:51:20, Oleg Nesterov wrote: > > > > > > > > Yes I agree, it would be nice to remove find_lock_task_mm(). And in > > > > fact it would be nice to kill task_struct->mm (but this needs a lot > > > > of cleanups). We probably want signal_struct->mm, but this is a bit > > > > complicated (locking). > > > > > > Is there any hard requirement to reset task_struct::mm in the first > > > place? > > > > Well, at least the scheduler needs this. > > Could you point me to where it depends on that? I mean if we are past > exit_mm then we have unmapped the address space most probably but why > should we care about that in the scheduler? There shouldn't be any > further access to the address space by that point. I can see that > context_switch() checks task->mm but it should just work when it sees it > non NULL, right? But who will do the final mmdrop() then? I am not saying this is impossible to change, say we do this in finish_task_switch(TASK_DEAD) or even in free_task(), but we do not want this? > Do you think this would be a way to go, though? We would have to special > case this because the mm_struct is quite large (~900B with my config) so > we would keep and pin it only for oom victims. Plus page tables, so it is more than 900B. But as I said, personally I agree with signal->oom_mm which can only be set by oom-killer. Oleg. -- 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