On Wed, Feb 18, 2009 at 09:11:51AM +0100, Gary Jennejohn wrote: > 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. > > > > Scott > > > > 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 > seeking. > I suppose on not extreme multi-core systems (ncores <= 4) buildworld is a good CPU test. For example: time make -j3 TARGET_ARCH=i386 buildworld [building] -------------------------------------------------------------- >>> World build completed on Wed Feb 18 11:59:28 CET 2009 -------------------------------------------------------------- 2163.449u 513.894s 24:17.49 183.6% 6113+2368k 26280+5968io 10602pf+0w ^^^^^^ This is on Core2Duo 3.0GHz with the single 500G WD SATA drive. Pre-caching src directory (with 'tar -cvf /dev/null src', for example) may speed up things by ~10%. Alexey.Received on Wed Feb 18 2009 - 10:16:47 UTC
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