HEADS UP: More CAM fixes.
gary.jennejohn at freenet.de
Wed Feb 18 00:12:08 PST 2009
On Tue, 17 Feb 2009 13:46:20 -0700
Scott Long <scottl at samsco.org> wrote:
> Bruce Evans wrote:
> > On Tue, 17 Feb 2009, Gary Jennejohn wrote:
> >> I tested this with an Adaptec 29160. I saw no real improvement in
> >> performance, but also no regressions.
> >> I suspect that the old disk I had attached just didn't have enough
> >> performance reserves to show an improvement.
> >> My test scenario was buildworld. Since /usr/src and /usr/obj were both
> >> on the one disk it got a pretty good workout.
> > ^^^^ low
> >> AMD64 X2 (2.5 GHz) with 4GB of RAM.
> > Buildworld hardly uses the disk at all. It reads and writes a few hundred
> > MB. Ideally the i/o should go at disk speeds of 50-200MB/S and thus take
> > between 20 and 5 seconds. In practice, it will take a few more seconds.
> > physically but perhaps even less virtually due to parallelism.
> > Bruce
> Yes, on modern machines, buildworld is bound almost completely by disk
> latency, and not at all by disk or controller bandwidth.
Maybe I misunderstood something, but I thought the patch was supposed
to improve queuing. Seems like all the seeks during a buildowrld
would exercise that. All I can say is that the disk did _lots_ of
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