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    SubjectRe: Linux 2.4.4-ac10
    On Fri, 18 May 2001, Rik van Riel wrote:

    > On Fri, 18 May 2001, Mike Galbraith wrote:
    > > On Thu, 17 May 2001, Rik van Riel wrote:
    > > > On Thu, 17 May 2001, Mike Galbraith wrote:
    > > >
    > > > > Only doing parallel kernel builds. Heavy load throughput is up,
    > > > > but it swaps too heavily. It's a little too conservative about
    > > > > releasing cache now imho. (keeping about double what it should be
    > > > > with this load.. easily [thump] tweaked;)
    > > >
    > > > "about double what it should be" ?
    > >
    > > Do you think there's 60-80mb of good cachable data? ;-) The "double"
    > > is based upon many hundreds of test runs. I "know" that performance
    > > is best with this load when the cache stays around 25-35Mb. I know
    > > this because I've done enough bend adjusting to get throughput to
    > > within one minute of single task times to have absolutely no doubt.
    > > I can get it to 30 seconds with much obscene tweaking, and have done
    > > it with zero additional overhead for make -j 30 ten times in a row.
    > > (that kernel was.. plain weird. perfect synchronization.. voodoo!)
    > Ahhh, I see. Remember that the "cached" figure you are
    > seeing also includes swap-cached data from the gccs, which
    > results from kswapd scanning the processes, clearing the
    > PTE and, a bit later, the process grabbing the page again.


    > I suspect that if the gccs _just_ fit in memory, you can
    > get some extra performance by mercilessly eating from the
    > cache and keeping the ggcs in memory. However, I also have
    > the sneaking suspicion that this is not the best tactic for
    > all workloads ;)

    Yes, ~exactly! I chose 30 tasks because they almost do (tool/userland
    dependant.. must recalibrate often) fit. The bitch is to get the vm
    to automagically detect the rss/cache munch tradeoff point without all
    the manual help.


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