On Fri, 16 Jun 2000, Mike Galbraith wrote:

On Wed, 14 Jun 2000, Alan Cox wrote:

quoted

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.

regards,

Rik
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