From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tetsuo Handa Subject: Re: [PATCH v7] mm: Add memory allocation watchdog kernel thread. Date: Thu, 9 Mar 2017 19:46:14 +0900 Message-ID: <201703091946.GDC21885.OQFFOtJHSOFVML@I-love.SAKURA.ne.jp> References: <1488244908-57586-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <1488244908-57586-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> Sender: linux-kernel-owner@vger.kernel.org To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, mhocko@kernel.org, hannes@cmpxchg.org, mgorman@techsingularity.net, david@fromorbit.com, apolyakov@beget.ru List-Id: linux-mm.kvack.org Andrew, do you have any questions on this patch? I really need this patch for finding bugs which MM people overlook. Tetsuo Handa wrote: > This patch adds a watchdog which periodically reports number of memory > allocating tasks, dying tasks and OOM victim tasks when some task is > spending too long time inside __alloc_pages_slowpath(). This patch also > serves as a hook for obtaining additional information using SystemTap > (e.g. examine other variables using printk(), capture a crash dump by > calling panic()) by triggering a callback only when a stall is detected. > Ability to take administrator-controlled actions based on some threshold > is a big advantage gained by introducing a state tracking. > > Commit 63f53dea0c9866e9 ("mm: warn about allocations which stall for > too long") was a great step for reducing possibility of silent hang up > problem caused by memory allocation stalls [1]. However, there are > reports of long stalls (e.g. [2] is over 30 minutes!) and lockups (e.g. > [3] is an "unable to invoke the OOM killer due to !__GFP_FS allocation" > lockup problem) where this patch is more useful than that commit, for > this patch can report possibly related tasks even if allocating tasks > are unexpectedly blocked for so long. Regarding premature OOM killer > invocation, tracepoints which can accumulate samples in short interval > would be useful. But regarding too late to report allocation stalls, > this patch which can capture all tasks (for reporting overall situation) > in longer interval and act as a trigger (for accumulating short interval > samples) would be useful.