From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f71.google.com (mail-oi0-f71.google.com [209.85.218.71]) by kanga.kvack.org (Postfix) with ESMTP id E88506B0033 for ; Wed, 13 Sep 2017 10:14:54 -0400 (EDT) Received: by mail-oi0-f71.google.com with SMTP id g15so415804oib.2 for ; Wed, 13 Sep 2017 07:14:54 -0700 (PDT) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [2001:e42:101:1:202:181:97:72]) by mx.google.com with ESMTPS id r64si8922944oib.355.2017.09.13.07.14.52 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 13 Sep 2017 07:14:53 -0700 (PDT) Subject: Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about stalls From: Tetsuo Handa References: <20170911082650.dqfirwc63xy7i33q@dhcp22.suse.cz> <20170913115442.4tpbiwu77y7lrz6g@dhcp22.suse.cz> <201709132254.DEE34807.LQOtMFOFJSOVHF@I-love.SAKURA.ne.jp> In-Reply-To: Message-Id: <201709132314.BID39077.HMFOJSLFtVOFOQ@I-love.SAKURA.ne.jp> Date: Wed, 13 Sep 2017 23:14:43 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: vbabka@suse.cz, mhocko@kernel.org, mpatocka@redhat.com Cc: hannes@cmpxchg.org, mgorman@suse.de, dave.hansen@intel.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Vlastimil Babka wrote: > On 09/13/2017 03:54 PM, Tetsuo Handa wrote: > > Michal Hocko wrote: > >> Let's see what others think about this. > > > > Whether __GFP_NOWARN should warn about stalls is not a topic to discuss. > > It is the topic of this thread, which tries to address a concrete > problem somebody has experienced. In that context, the rest of your > concerns seem to me not related to this problem, IMHO. I suggested replacing warn_alloc() with safe/useful one rather than tweaking warn_alloc() about __GFP_NOWARN. > > > I consider warn_alloc() for reporting stalls is broken. It fails to provide > > backtrace of stalling location. For example, OOM lockup with oom_lock held > > cannot be reported by warn_alloc(). It fails to provide readable output when > > called concurrently. For example, concurrent calls can cause printk()/ > > schedule_timeout_killable() lockup with oom_lock held. printk() offloading is > > not an option, for there will be situations where printk() offloading cannot > > be used (e.g. queuing via printk() is faster than writing to serial consoles > > which results in unreadable logs due to log_bug overflow). -- 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