From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx172.postini.com [74.125.245.172]) by kanga.kvack.org (Postfix) with SMTP id 447216B0002 for ; Fri, 12 Apr 2013 17:14:43 -0400 (EDT) Message-ID: <51687940.8090006@bitsync.net> Date: Fri, 12 Apr 2013 23:14:40 +0200 From: Zlatko Calusic MIME-Version: 1.0 Subject: Re: [PATCH 0/10] Reduce system disruption due to kswapd V2 References: <1365505625-9460-1-git-send-email-mgorman@suse.de> <51672331.6070605@bitsync.net> <20130412193947.GJ11656@suse.de> <5168699A.40407@bitsync.net> <20130412204129.GA13146@suse.de> In-Reply-To: <20130412204129.GA13146@suse.de> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Andrew Morton , Jiri Slaby , Valdis Kletnieks , Rik van Riel , Johannes Weiner , dormando , Michal Hocko , Linux-MM , LKML On 12.04.2013 22:41, Mel Gorman wrote: > On Fri, Apr 12, 2013 at 10:07:54PM +0200, Zlatko Calusic wrote: >> On 12.04.2013 21:40, Mel Gorman wrote: >>> On Thu, Apr 11, 2013 at 10:55:13PM +0200, Zlatko Calusic wrote: >>>> On 09.04.2013 13:06, Mel Gorman wrote: >>>> >>>> >>>> - The only slightly negative thing I observed is that with the patch >>>> applied kswapd burns 10x - 20x more CPU. So instead of about 15 >>>> seconds, it has now spent more than 4 minutes on one particular >>>> machine with a quite steady load (after about 12 days of uptime). >>>> Admittedly, that's still nothing too alarming, but... >>>> >>> >>> Would you happen to know what circumstances trigger the higher CPU >>> usage? >>> >> >> Really nothing special. The server is lightly loaded, but it does >> enough reading from the disk so that pagecache is mostly populated >> and page reclaiming is active. So, kswapd is no doubt using CPU time >> gradually, nothing extraordinary. >> >> When I sent my reply yesterday, the server uptime was 12 days, and >> kswapd had accumulated 4:28 CPU time. Now, approx 24 hours later (13 >> days uptime): >> >> root 23 0.0 0.0 0 0 ? S Mar30 4:52 [kswapd0] >> > > Ok, that's not too crazy. > Certainly. >> I will apply your v3 series soon and see if there's any improvement >> wrt CPU usage, although as I said I don't see that as a big issue. >> It's still only 0.013% of available CPU resources (dual core CPU). >> > > Excellent, thanks very much for testing and reporting back. The pleasure is all mine. I really admire your work. > I read your > mail on the zone balancing and FWIW I would not have expected this series > to have any impact on it. Good to know. At first I thought that your changes on the anon/file balance could make something different, obviously not. > I do not have a good theory yet as to what the > problem is but I'll give it some thought and se what I come up with. I'll > be at LSF/MM next week so it might take me a while. > Yeah, that's definitely not something to be solved quickly, let it wait until you have more time, and I'll also continue to test various things after a slight break. It's a quite subtle issue, although the solution will probably be simple and obvious. But, I also think it'll take a lot of time to find it. I tried to develop an artificial test case to speed up debugging, but failed horribly. It seems that the issue can be seen only on real workloads. -- 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