From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id E08EB6B026E for ; Wed, 10 Oct 2018 08:25:43 -0400 (EDT) Received: by mail-ed1-f71.google.com with SMTP id h24-v6so3077625eda.10 for ; Wed, 10 Oct 2018 05:25:43 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id e44-v6si14794407edd.247.2018.10.10.05.25.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Oct 2018 05:25:42 -0700 (PDT) Date: Wed, 10 Oct 2018 14:25:39 +0200 From: Michal Hocko 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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