linux-kernel - Re: Linux Software RAID 5 Performance Optimizations: 2.6.19.1: (211MB/s read & 195MB/s write)

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Date:	Fri, 12 Jan 2007 22:49:13 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	Justin Piszcz <jpiszcz@...idpixels.com>
Cc:	linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
	xfs@....sgi.com
Subject: Re: Linux Software RAID 5 Performance Optimizations: 2.6.19.1: (211MB/s read & 195MB/s write)

Justin Piszcz wrote:
> RAID 5 TWEAKED: 1:06.41 elapsed @ 60% CPU
>
> This should be 1:14 not 1:06(was with a similarly sized file but not the
> same) the 1:14 is the same file as used with the other benchmarks.  and to
> get that I used 256mb read-ahead and 16384 stripe size ++ 128
> max_sectors_kb (same size as my sw raid5 chunk size)

max_sectors_kb is probably your key. On my system I get twice the read 
performance by just reducing max_sectors_kb from default 512 to 192.

Can you do a fresh reboot to shell and then:
$ cat /sys/block/hda/queue/*
$ cat /proc/meminfo
$ echo 3 > /proc/sys/vm/drop_caches
$ dd if=/dev/hda of=/dev/null bs=1M count=10240
$ echo 192 > /sys/block/hda/queue/max_sectors_kb
$ echo 3 > /proc/sys/vm/drop_caches
$ dd if=/dev/hda of=/dev/null bs=1M count=10240


Thanks!

--
Al

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