From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 281086B0033 for ; Fri, 15 Sep 2017 08:14:06 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id e64so2984778wmi.0 for ; Fri, 15 Sep 2017 05:14:06 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id g91si1051387ede.460.2017.09.15.05.14.04 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 15 Sep 2017 05:14:04 -0700 (PDT) Date: Fri, 15 Sep 2017 14:14:01 +0200 From: Michal Hocko Subject: Re: [PATCH] mm,page_alloc: softlockup on warn_alloc on Message-ID: <20170915121401.eaoncsmahh2stqn2@dhcp22.suse.cz> References: <20170915095849.9927-1-yuwang668899@gmail.com> <20170915103957.64r5xln7s6wlu3ro@dhcp22.suse.cz> <201709152038.BHF26323.LFOMFHOFOJSVQt@I-love.SAKURA.ne.jp> <20170915120020.diakzyzsx73ygnfx@dhcp22.suse.cz> <201709152109.AID48261.FtHOFMFQOJVLOS@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201709152109.AID48261.FtHOFMFQOJVLOS@I-love.SAKURA.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: yuwang668899@gmail.com, vbabka@suse.cz, mpatocka@redhat.com, hannes@cmpxchg.org, mgorman@suse.de, dave.hansen@intel.com, akpm@linux-foundation.org, linux-mm@kvack.org, chenggang.qcg@alibaba-inc.com, yuwang.yuwang@alibaba-inc.com On Fri 15-09-17 21:09:29, Tetsuo Handa wrote: > Michal Hocko wrote: > > On Fri 15-09-17 20:38:49, Tetsuo Handa wrote: > > [...] > > > You said "identify _why_ we see the lockup trigerring in the first > > > place" without providing means to identify it. Unless you provide > > > means to identify it (in a form which can be immediately and easily > > > backported to 4.9 kernels; that is, backporting not-yet-accepted > > > printk() offloading patchset is not a choice), this patch cannot be > > > refused. > > > > I fail to see why. It simply workarounds an existing problem elsewhere > > in the kernel without deeper understanding on where the problem is. You > > can add your own instrumentation to debug and describe the problem. This > > is no different to any other kernel bugs... > > Please do show us your patch for that. Normal users cannot afford developing > such instrumentation to debug and describe the problem. Stop this nonsense already! Any kernel bug/lockup needs a debugging which might be non-trivial and it is necessary to understand the real culprit. We do not add random hacks to silence a problem. We aim at fixing it! > > If our printk implementation is so weak it cannot cope with writers then > > that should be fixed without spreading hacks in different subsystems. If > > the lockup is a real problem under normal workloads (rather than > > artificial ones) then we should try to throttle more aggresively. > > No throttle please. Throttling makes warn_alloc() more and more useless. so does try_lock approach... -- Michal Hocko SUSE Labs -- 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