From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f69.google.com (mail-it0-f69.google.com [209.85.214.69]) by kanga.kvack.org (Postfix) with ESMTP id 799956B0033 for ; Fri, 15 Sep 2017 07:55:41 -0400 (EDT) Received: by mail-it0-f69.google.com with SMTP id d6so5776300itc.6 for ; Fri, 15 Sep 2017 04:55:41 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id j131si477187oia.148.2017.09.15.04.55.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Sep 2017 04:55:39 -0700 (PDT) Subject: Re: Detecting page cache trashing state References: <150543458765.3781.10192373650821598320@takondra-t460s> From: Zdenek Kabelac Message-ID: <20733be8-6038-434f-c50f-0a57616ebe47@redhat.com> Date: Fri, 15 Sep 2017 13:55:37 +0200 MIME-Version: 1.0 In-Reply-To: <150543458765.3781.10192373650821598320@takondra-t460s> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Taras Kondratiuk , linux-mm@kvack.org Cc: xe-linux-external@cisco.com, Ruslan Ruslichenko , linux-kernel@vger.kernel.org Dne 15.9.2017 v 02:16 Taras Kondratiuk napsal(a): > Hi > > In our devices under low memory conditions we often get into a trashing > state when system spends most of the time re-reading pages of .text > sections from a file system (squashfs in our case). Working set doesn't > fit into available page cache, so it is expected. The issue is that > OOM killer doesn't get triggered because there is still memory for > reclaiming. System may stuck in this state for a quite some time and > usually dies because of watchdogs. > > We are trying to detect such trashing state early to take some > preventive actions. It should be a pretty common issue, but for now we > haven't find any existing VM/IO statistics that can reliably detect such > state. > > Most of metrics provide absolute values: number/rate of page faults, > rate of IO operations, number of stolen pages, etc. For a specific > device configuration we can determine threshold values for those > parameters that will detect trashing state, but it is not feasible for > hundreds of device configurations. > > We are looking for some relative metric like "percent of CPU time spent > handling major page faults". With such relative metric we could use a > common threshold across all devices. For now we have added such metric > to /proc/stat in our kernel, but we would like to find some mechanism > available in upstream kernel. > > Has somebody faced similar issue? How are you solving it? > Hi Well I witness this when running Firefox & Thunderbird on my desktop for a while on just 4G RAM machine till these 2app eat all free RAM... It gets to the position (when I open new tab) that mouse hardly moves - kswapd eats CPU (I've no swap in fact - so likely just page-caching). The only 'quick' solution for me as desktop user is to manually invoke OOM with SYSRQ+F key - and I'm also wondering why the system is not reacting better. In most cases it kills one of those 2 - but sometime it kills whole Xsession... Regards Zdenek -- 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