From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f199.google.com (mail-ob0-f199.google.com [209.85.214.199]) by kanga.kvack.org (Postfix) with ESMTP id A006B6B0005 for ; Thu, 19 May 2016 21:30:57 -0400 (EDT) Received: by mail-ob0-f199.google.com with SMTP id dh6so166532943obb.1 for ; Thu, 19 May 2016 18:30:57 -0700 (PDT) Received: from lgeamrelo13.lge.com (LGEAMRELO13.lge.com. [156.147.23.53]) by mx.google.com with ESMTP id fp9si2027569igb.56.2016.05.19.18.30.55 for ; Thu, 19 May 2016 18:30:56 -0700 (PDT) Date: Fri, 20 May 2016 10:30:53 +0900 From: Minchan Kim Subject: Re: [PATCH 2/2] mm, oom_reaper: do not mmput synchronously from the oom reaper context Message-ID: <20160520013053.GB2224@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , Tetsuo Handa , David Rientjes , linux-mm@kvack.org, LKML , Michal Hocko Forking new thread because my comment is not related to this patch's purpose but found a thing during reading this patch. On Tue, Apr 26, 2016 at 04:04:30PM +0200, Michal Hocko wrote: > From: Michal Hocko > > Tetsuo has properly noted that mmput slow path might get blocked waiting > for another party (e.g. exit_aio waits for an IO). If that happens the > oom_reaper would be put out of the way and will not be able to process > next oom victim. We should strive for making this context as reliable > and independent on other subsystems as much as possible. > > Introduce mmput_async which will perform the slow path from an async > (WQ) context. This will delay the operation but that shouldn't be a > problem because the oom_reaper has reclaimed the victim's address space > for most cases as much as possible and the remaining context shouldn't > bind too much memory anymore. The only exception is when mmap_sem > trylock has failed which shouldn't happen too often. > > The issue is only theoretical but not impossible. The mmput_async is used for only OOM reaper which is enabled on CONFIG_MMU. So until someone who want to use mmput_async in !CONFIG_MMU come out, we could save sizeof(struct work_struct) per mm in !CONFIG_MMU. -- 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