Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754597AbaAUMk4 (ORCPT ); Tue, 21 Jan 2014 07:40:56 -0500 Received: from szxga01-in.huawei.com ([119.145.14.64]:17504 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754289AbaAUMkx (ORCPT ); Tue, 21 Jan 2014 07:40:53 -0500 Message-ID: <52DE6AA0.1000801@huawei.com> Date: Tue, 21 Jan 2014 20:40:00 +0800 From: Jianguo Wu User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: David Rientjes CC: Andrew Morton , Johannes Weiner , Rik van Riel , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: Re: [question] how to figure out OOM reason? should dump slab/vmalloc info when OOM? References: <52DCFC33.80008@huawei.com> In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.24.155] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014/1/21 13:34, David Rientjes wrote: > On Mon, 20 Jan 2014, Jianguo Wu wrote: > >> When OOM happen, will dump buddy free areas info, hugetlb pages info, >> memory state of all eligible tasks, per-cpu memory info. >> But do not dump slab/vmalloc info, sometime, it's not enough to figure out the >> reason OOM happened. >> >> So, my questions are: >> 1. Should dump slab/vmalloc info when OOM happen? Though we can get these from proc file, >> but usually we do not monitor the logs and check proc file immediately when OOM happened. >> > Hi David, Thank you for your patience to answer! > The problem is that slabinfo becomes excessively verbose and dumping it > all to the kernel log often times causes important messages to be lost. > This is why we control things like the tasklist dump with a VM sysctl. It > would be possible to dump, say, the top ten slab caches with the highest > memory usage, but it will only be helpful for slab leaks. Typically there > are better debugging tools available than analyzing the kernel log; if you > see unusually high slab memory in the meminfo dump, you can enable it. > But, when OOM has happened, we can only use kernel log, slab/vmalloc info from proc is stale. Maybe we can dump slab/vmalloc with a VM sysctl, and only top 10/20 entrys? Thanks. >> 2. /proc/$pid/smaps and pagecache info also helpful when OOM, should also be dumped? >> > > Also very verbose and would cause important messages to be lost, we try to > avoid spamming the kernel log with all of this information as much as > possible. > >> 3. Without these info, usually how to figure out OOM reason? >> > > Analyze the memory usage in the meminfo and determine what is unusually > high; if it's mostly anonymous memory, you can usually correlate it back > to a high rss for a process in the tasklist that you didn't suspect to be > using that much memory, for example. > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/