Re: [PATCH 0/10] Reduce system disruption due to kswapd V2

[Zlatko Calusic]

On 22.04.2013 08:43, Simon Jeons wrote:
> Hi Zlatko,
> On 04/22/2013 02:37 PM, Zlatko Calusic wrote:
> > 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.
>
> Could you tell me how you draw this picture?

It's a home made server monitoring system. I just added the code needed 
to graph the size of active + inactive LRU lists, per zone and per type. 
Check out http://oss.oetiker.ch/rrdtool/

--
Zlatko

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