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

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Date:	Sat, 13 Jan 2007 00:00:48 +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:
> Btw, max sectors did improve my performance a little bit but
> stripe_cache+read_ahead were the main optimizations that made everything
> go faster by about ~1.5x.   I have individual bonnie++ benchmarks of
> [only] the max_sector_kb tests as well, it improved the times from
> 8min/bonnie run -> 7min 11 seconds or so, see below and then after that is
> what you requested.
>
> # echo 3 > /proc/sys/vm/drop_caches
> # dd if=/dev/md3 of=/dev/null bs=1M count=10240
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB) copied, 399.352 seconds, 26.9 MB/s
> # for i in sde sdg sdi sdk; do   echo 192 >
> /sys/block/"$i"/queue/max_sectors_kb;   echo "Set
> /sys/block/"$i"/queue/max_sectors_kb to 192kb"; done
> Set /sys/block/sde/queue/max_sectors_kb to 192kb
> Set /sys/block/sdg/queue/max_sectors_kb to 192kb
> Set /sys/block/sdi/queue/max_sectors_kb to 192kb
> Set /sys/block/sdk/queue/max_sectors_kb to 192kb
> # echo 3 > /proc/sys/vm/drop_caches
> # dd if=/dev/md3 of=/dev/null bs=1M count=10240
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB) copied, 398.069 seconds, 27.0 MB/s
>
> Awful performance with your numbers/drop_caches settings.. !

Can you repeat with /dev/sda only?

With fresh reboot to shell, then:
$ cat /sys/block/sda/queue/max_sectors_kb
$ echo 3 > /proc/sys/vm/drop_caches
$ dd if=/dev/sda of=/dev/null bs=1M count=10240

$ echo 192 > /sys/block/sda/queue/max_sectors_kb
$ echo 3 > /proc/sys/vm/drop_caches
$ dd if=/dev/sda of=/dev/null bs=1M count=10240

$ echo 128 > /sys/block/sda/queue/max_sectors_kb
$ echo 3 > /proc/sys/vm/drop_caches
$ dd if=/dev/sda of=/dev/null bs=1M count=10240

> What were your tests designed to show?

A problem with the block-io.


Thanks!

--
Al

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