Re: kswapd eating too much CPU on ac16/ac18

Mike Galbraith
2000-06-18T06:26:56Z

On Fri, 16 Jun 2000, Rik van Riel wrote:

> On Fri, 16 Jun 2000, Mike Galbraith wrote:
> > On Wed, 14 Jun 2000, Alan Cox wrote:
> >
> > > Im interested to know if ac9/ac10 is the slow->fast change point
> >
> > ac5 is definately the breaking point. ac5 doesn't survive make
> > -j30.. starts swinging it's VM machette at everything in sight.
> > Reversing the VM changes to ac4 restores throughput to test1
> > levels (11 minute build vs 21-26 minutes for everything
> > forward).
> >
> > Exact tested reversals below. FWIW, page aging doesn't seem to
> > be the problem. I disabled that in ac17 and saw zero
> > difference. (What may or not be a hint is that the /* Let
> > shrink_mmap handle this swapout. */ bit in vmscan.c does make a
> > consistent difference. Reverting that bit alone takes a minimum
> > of 4 minutes off build time)
>
> Interesting. Not delaying the swapout IO completely broke
> performance under the tests I did here...
>
> Delayed swapout vs. non-delayed swapouts was the difference
> between 300 swapouts/s vs. 700 swapouts/s (under a load
> with 400 swapins/s).
>
> OTOH, I can imagine it being better if you have a very small
> LRU cache, something like less than 1/2 MB.

Removing only the hunk identified by Roger Larsonn brought ac20 performance
beyond 99-pre5 :) Reverting deferred swap also no longer helps at all
and in fact hurts slightly (30 sec difference on make -j30 build times)

-Mike

(shoot.. if it kicks butt now, I wonder what adding Juan's patch will do:)