From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f47.google.com (mail-pa0-f47.google.com [209.85.220.47]) by kanga.kvack.org (Postfix) with ESMTP id 74FDA6B0032 for ; Wed, 7 Jan 2015 20:04:29 -0500 (EST) Received: by mail-pa0-f47.google.com with SMTP id kq14so8302338pab.6 for ; Wed, 07 Jan 2015 17:04:29 -0800 (PST) Received: from peace.netnation.com (peace.netnation.com. [204.174.223.2]) by mx.google.com with ESMTP id wq3si5890749pbc.91.2015.01.07.17.04.27 for ; Wed, 07 Jan 2015 17:04:28 -0800 (PST) Date: Wed, 7 Jan 2015 17:04:26 -0800 From: Simon Kirby Subject: Re: Dirty pages underflow on 3.14.23 Message-ID: <20150108010426.GB6664@hostway.ca> References: <20150106150250.GA26895@phnom.home.cmpxchg.org> <20150107212858.GA6664@hostway.ca> <54ADA99A.90501@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54ADA99A.90501@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Holger Hoffst?tte , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed, Jan 07, 2015 at 10:48:10PM +0100, Vlastimil Babka wrote: > On 01/07/2015 10:28 PM, Simon Kirby wrote: > > > Hmm...A possibly-related issue...Before trying this, after a fresh boot, > > /proc/vmstat showed: > > > > nr_alloc_batch 4294541205 > > This can happen, and not be a problem in general. However, there was a fix > abe5f972912d086c080be4bde67750630b6fb38b in 3.17 for a potential performance > issue if this counter overflows on single processor configuration. It was marked > stable, but the 3.16 series was discontinued before the fix could be backported. > So if you are on single-core, you might hit the performance issue. That particular commit seems to just change the code path in that case, but should it be underflowing at all on UP? > > Still, nr_alloc_batch reads as 4294254379 after MySQL restart, and now > > seems to stay up there. > > Hm if it stays there, then you are probably hitting the performance issue. Look > at /proc/zoneinfo, which zone has the underflow. It means this zone will get > unfair amount of allocations, while others may contain stale data and would be > better candidates. In this case, it has only 640MB, and there's only DMA and Normal. This is affecting Normal, and DMA is so small that it probably doesn't matter. Simon- -- 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