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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C2A8C43441 for ; Wed, 10 Oct 2018 12:25:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E8CBC20858 for ; Wed, 10 Oct 2018 12:25:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8CBC20858 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726825AbeJJTrj (ORCPT ); Wed, 10 Oct 2018 15:47:39 -0400 Received: from mx2.suse.de ([195.135.220.15]:38414 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726649AbeJJTrj (ORCPT ); Wed, 10 Oct 2018 15:47:39 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7D4B9B091; Wed, 10 Oct 2018 12:25:41 +0000 (UTC) Date: Wed, 10 Oct 2018 14:25:39 +0200 From: Michal Hocko To: Sergey Senozhatsky Cc: Tetsuo Handa , syzbot , hannes@cmpxchg.org, akpm@linux-foundation.org, guro@fb.com, kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, rientjes@google.com, syzkaller-bugs@googlegroups.com, yang.s@alibaba-inc.com, Sergey Senozhatsky , Petr Mladek Subject: Re: INFO: rcu detected stall in shmem_fault Message-ID: <20181010122539.GI5873@dhcp22.suse.cz> References: <000000000000dc48d40577d4a587@google.com> <201810100012.w9A0Cjtn047782@www262.sakura.ne.jp> <20181010085945.GC5873@dhcp22.suse.cz> <20181010113500.GH5873@dhcp22.suse.cz> <20181010114833.GB3949@tigerII.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181010114833.GB3949@tigerII.localdomain> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 10-10-18 20:48:33, Sergey Senozhatsky wrote: > On (10/10/18 13:35), Michal Hocko wrote: > > > Just flooding out of memory messages can trigger RCU stall problems. > > > For example, a severe skbuff_head_cache or kmalloc-512 leak bug is causing > > > > [...] > > > > Quite some of them, indeed! I guess we want to rate limit the output. > > What about the following? > > A bit unrelated, but while we are at it: > > I like it when we rate-limit printk-s that lookup the system. > But it seems that default rate-limit values are not always good enough, > DEFAULT_RATELIMIT_INTERVAL / DEFAULT_RATELIMIT_BURST can still be too > verbose. For instance, when we have a very slow IPMI emulated serial > console -- e.g. baud rate at 57600. DEFAULT_RATELIMIT_INTERVAL and > DEFAULT_RATELIMIT_BURST can add new OOM headers and backtraces faster > than we evict them. > > Does it sound reasonable enough to use larger than default rate-limits > for printk-s in OOM print-outs? OOM reports tend to be somewhat large > and the reported numbers are not always *very* unique. > > What do you think? I do not really care about the current inerval/burst values. This change should be done seprately and ideally with some numbers. -- Michal Hocko SUSE Labs