From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756825AbbCMPXT (ORCPT ); Fri, 13 Mar 2015 11:23:19 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:45873 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752804AbbCMPXP (ORCPT ); Fri, 13 Mar 2015 11:23:15 -0400 Date: Fri, 13 Mar 2015 16:23:11 +0100 From: Michal Hocko To: Vaibhav Shinde Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Mel Gorman Subject: Re: kswapd hogging in lowmem_shrink Message-ID: <20150313152311.GF4881@dhcp22.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 13-03-15 19:55:27, Vaibhav Shinde wrote: > On low memory situation, I see various shrinkers being invoked, but in > lowmem_shrink() case, kswapd is found to be hogging for around 150msecs. > > Due to this my application suffer latency issue, as the cpu was not > released by kswapd0. > > I took below traces with vmscan events, that show lowmem_shrink taking such > long time for execution. > > kswapd0-67 [003] ...1 1501.987110: mm_shrink_slab_start: > lowmem_shrink+0x0/0x580 c0ee8e34: objects to shrink 122 gfp_flags > GFP_KERNEL pgs_scanned 83 lru_pgs 241753 cache items 241754 delta 10 > total_scan 132 > kswapd0-67 [003] ...1 1502.020827: mm_shrink_slab_end: > lowmem_shrink+0x0/0x580 c0ee8e34: unused scan count 122 new scan count 4 > total_scan -118 last shrinker return val 237339 > > Please provide inputs on the same. I would strongly discourage from using lowmemory killer. It is broken by design IMHO. It can spend a lot of time looping on a large machine. Why do you use it in the first place? -- Michal Hocko SUSE Labs