From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by kanga.kvack.org (Postfix) with ESMTP id A0C7F6B0269 for ; Wed, 10 Oct 2018 07:48:50 -0400 (EDT) Received: by mail-pg1-f198.google.com with SMTP id e6-v6so3320981pge.5 for ; Wed, 10 Oct 2018 04:48:50 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id u2-v6sor16747333plq.31.2018.10.10.04.48.49 for (Google Transport Security); Wed, 10 Oct 2018 04:48:49 -0700 (PDT) From: Sergey Senozhatsky Date: Wed, 10 Oct 2018 20:48:33 +0900 Subject: Re: INFO: rcu detected stall in shmem_fault Message-ID: <20181010114833.GB3949@tigerII.localdomain> References: <000000000000dc48d40577d4a587@google.com> <201810100012.w9A0Cjtn047782@www262.sakura.ne.jp> <20181010085945.GC5873@dhcp22.suse.cz> <20181010113500.GH5873@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181010113500.GH5873@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko 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 , Sergey Senozhatsky , Petr Mladek 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? -ss