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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 A73DEC43441 for ; Wed, 10 Oct 2018 12:30:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C94B2085B for ; Wed, 10 Oct 2018 12:30:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="p/V2B+KR" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6C94B2085B Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com 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 S1726727AbeJJTv7 (ORCPT ); Wed, 10 Oct 2018 15:51:59 -0400 Received: from mail-it1-f196.google.com ([209.85.166.196]:37174 "EHLO mail-it1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726503AbeJJTv7 (ORCPT ); Wed, 10 Oct 2018 15:51:59 -0400 Received: by mail-it1-f196.google.com with SMTP id e74-v6so7653918ita.2 for ; Wed, 10 Oct 2018 05:30:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=O0TqrtLynyOzG0Q8a1r+9ryCvb0PwuY8Q+HlWlOqKx0=; b=p/V2B+KRHmhZ9Y9x39tDlCaNMIQQR3I4UxwCSo7aB4yUIUYmseTn5XnGpKk8HfV7wB th6bwn5NWwP97hWKV0AZIDgPwWK0xqwZAD/tb8tzB6i1Tjw6sc0ptaEKn+38n6LZh71a dHdy0dJuRDecm47lhneJjjSTp36N+BKijLmsZxPtps2EgzY5YUctehrGV9MoQMyp8d9K Wvr5YxgBye6ij6e5F2PVsNu5WAbi7aJr8mxyocVonJSAp5gurjmUg/SCOb0AWje7v1Ss i14HCKB8U+53PCnHKhiO6rDlf8lAoy5RrWJY/9VHF6C/YO0wjbXDe3KEyq1EJaYOMEBq F+nQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=O0TqrtLynyOzG0Q8a1r+9ryCvb0PwuY8Q+HlWlOqKx0=; b=pHMyLUyiDaXs4RDVuvL5c+NMeHWMl+EmBpd7RYlDW0XNeFGtHyJAVo9x1uKNWlHgGs jzHvSiXj1tG2jmF6Hj1px2wJrVnjyYBzJBe+Jc3TEZC75qL/xCSnYt86w+9EXGrTi2tq 2ka1GStEQ7GtJfMcNB8pHui99hFW1q8yf9efQwlieO6bwQwbyaM57+lCrhaRO/8mnqNP tgaUPWRHO8dm7PRxuxqFPviXlAx2V6sJyxkuNp6feekIysdVIxYsfEzTH7n7kQXng3R0 Y5+rxjZFnj/0aWzbCUHAKrpHy57Y4aKrXcN5qOSHQOc3kORrrDzGy1UBhNYJ1fCOejCG 5M3A== X-Gm-Message-State: ABuFfoj+EPI3G1/LE2ZONoiqR3zGInr7BAAnZffdm1PYV3+aeZJ4xa6l pPaDwVYJK2LaSsmEBJv06Rosn1e5IXjAJ8fhkWb3Hw== X-Google-Smtp-Source: ACcGV634IBVxjt8ovIeJas+Lra+md9jIMTLi3AfFyycIbj+ErfxxJ+B8E98KBjlJ14QkEPy1NP95QqI2jNccwdTy40E= X-Received: by 2002:a24:f584:: with SMTP id k126-v6mr511529ith.166.1539174600624; Wed, 10 Oct 2018 05:30:00 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a02:1003:0:0:0:0:0 with HTTP; Wed, 10 Oct 2018 05:29:40 -0700 (PDT) In-Reply-To: <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> <20181010122539.GI5873@dhcp22.suse.cz> From: Dmitry Vyukov Date: Wed, 10 Oct 2018 14:29:40 +0200 Message-ID: Subject: Re: INFO: rcu detected stall in shmem_fault To: Michal Hocko Cc: Sergey Senozhatsky , Tetsuo Handa , syzbot , Johannes Weiner , Andrew Morton , guro@fb.com, "Kirill A. Shutemov" , LKML , Linux-MM , David Rientjes , syzkaller-bugs , Yang Shi , Sergey Senozhatsky , Petr Mladek Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 10, 2018 at 2:25 PM, Michal Hocko wrote: > 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. I think Sergey meant that this place may need to use larger-than-default values because it prints lots of output per instance (whereas the default limit is more tuned for cases that print just 1 line). I've found at least 1 place that uses DEFAULT_RATELIMIT_INTERVAL*10: https://elixir.bootlin.com/linux/latest/source/fs/btrfs/extent-tree.c#L8365 Probably we need something similar here.