Messages in this thread | | | Date | Mon, 22 Apr 2013 08:37:03 +0200 | From | Zlatko Calusic <> | Subject | Re: [PATCH 0/10] Reduce system disruption due to kswapd V2 |
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On 12.04.2013 22:07, 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: >>> <SNIP> >>> >>> - 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] > > 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). >
JFTR, v3 kswapd uses about 15% more CPU time than v2. 2:50 kswapd CPU time after 6 days 14h uptime.
And find attached another debugging graph that shows how ANON pages are privileged in the ZONE_NORMAL on a 4GB machine. Take notice that the number of pages in the ZONE_DMA32 is scaled (/5) to fit the graph nicely.
-- Zlatko [unhandled content-type:image/png] | |