From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx103.postini.com [74.125.245.103]) by kanga.kvack.org (Postfix) with SMTP id 6EB956B0031 for ; Wed, 31 Jul 2013 05:33:42 -0400 (EDT) Message-ID: <51F8D9F3.4040108@bitsync.net> Date: Wed, 31 Jul 2013 11:33:39 +0200 From: Zlatko Calusic MIME-Version: 1.0 Subject: Re: [patch 0/3] mm: improve page aging fairness between zones/nodes References: <1374267325-22865-1-git-send-email-hannes@cmpxchg.org> <51ED6274.3000509@bitsync.net> <51EFB80B.1090302@bitsync.net> In-Reply-To: <51EFB80B.1090302@bitsync.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Andrew Morton , Mel Gorman , Rik van Riel , Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 24.07.2013 13:18, Zlatko Calusic wrote: > On 22.07.2013 18:48, Zlatko Calusic wrote: >> On 19.07.2013 22:55, Johannes Weiner wrote: >>> The way the page allocator interacts with kswapd creates aging >>> imbalances, where the amount of time a userspace page gets in memory >>> under reclaim pressure is dependent on which zone, which node the >>> allocator took the page frame from. >>> >>> #1 fixes missed kswapd wakeups on NUMA systems, which lead to some >>> nodes falling behind for a full reclaim cycle relative to the other >>> nodes in the system >>> >>> #3 fixes an interaction where kswapd and a continuous stream of page >>> allocations keep the preferred zone of a task between the high and >>> low watermark (allocations succeed + kswapd does not go to sleep) >>> indefinitely, completely underutilizing the lower zones and >>> thrashing on the preferred zone >>> >>> These patches are the aging fairness part of the thrash-detection >>> based file LRU balancing. Andrea recommended to submit them >>> separately as they are bugfixes in their own right. >>> >> >> I have the patch applied and under testing. So far, so good. It looks >> like it could finally fix the bug that I was chasing few months ago >> (nicely described in your bullet #3). But, few more days of testing will >> be needed before I can reach a quality verdict. >> > > Well, only 2 days later it's already obvious that the patch is perfect! :) > Additionaly, on the patched kernel, kswapd burns 30% less CPU cycles. Nice to see that restored balance also eases kswapd's job, but that was to be expected. Measured on the real workload, twice, to be sure. Regards, -- Zlatko -- 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