Re: kswapd eating too much CPU on ac16/ac18

[Mike Galbraith <mikeg@weiden.de>]

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:)

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