Re: kswapd eating too much CPU on ac16/ac18

From: Rik van Riel (
Date: Fri Jun 16 2000 - 10:08:06 EST

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.



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