Guy wrote:
-----Original Message-----
From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid-
owner@xxxxxxxxxxxxxxx] On Behalf Of Bill Davidsen
Sent: Wednesday, September 28, 2005 4:05 PM
To: Guy
Cc: 'Holger Kiehl'; 'Mark Hahn'; 'linux-raid'; 'linux-kernel'
Subject: Re: Where is the performance bottleneck?
Guy wrote:
In most of your results, your CPU usage is very high. Once you get to
about
90% usage, you really can't do much else, unless you can improve the CPU
usage.
That seems one of the problems with software RAID, the calculations are
done in the CPU and not dedicated hardware. As you move to the top end
drive hardware the CPU gets to be a limit. I don't remember off the top
of my head how threaded this code is, and if more CPUs will help.
My old 500MHz P3 can xor at 1GB/sec. I don't think the RAID5 logic is the
issue! Also, I have not seen hardware that fast! Or even half as fast.
But I must admit, I have not seen a hardware RAID5 in a few years. :(
8regs : 918.000 MB/sec
32regs : 469.600 MB/sec
pIII_sse : 994.800 MB/sec
pII_mmx : 1102.400 MB/sec
p5_mmx : 1152.800 MB/sec
raid5: using function: pIII_sse (994.800 MB/sec)
Humm.. It did not select the fastest?
Maybe. There was discussion on this previously, but the decision was
made to us sse when available because it is nicer to cache, or uses
fewer registers, or similar. In any case fewer undesirable side effects.
--
bill davidsen <davidsen@xxxxxxx>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
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