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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Subject: Re: [PATCH] readahead:add blk_run_backing_dev
Cc: kosaki.motohiro@jp.fujitsu.com, Wu Fengguang <fengguang.wu@intel.com>,
       Andrew Morton <akpm@linux-foundation.org>,
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Date: Wed, 27 May 2009 12:26:38 +0900 (JST)
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> >> >The numbers look too small for a 7 disk RAID:
> >> >
> >> >        > #dd if=testdir/testfile of=/dev/null bs=16384
> >> >        >
> >> >        > -2.6.30-rc6
> >> >        > 1048576+0 records in
> >> >        > 1048576+0 records out
> >> >        > 17179869184 bytes (17 GB) copied, 224.182 seconds, 76.6 MB/s
> >> >        >
> >> >        > -2.6.30-rc6-patched
> >> >        > 1048576+0 records in
> >> >        > 1048576+0 records out
> >> >        > 17179869184 bytes (17 GB) copied, 206.465 seconds, 83.2 MB/s
> >> >
> >> >I'd suggest you to configure the array properly before coming back to
> >> >measuring the impact of this patch.
> >> 
> >> 
> >> I created 16GB file to this disk array, and mounted to testdir, dd to 
> >this directory.
> >
> >I mean, you should get >300MB/s throughput with 7 disks, and you
> >should seek ways to achieve that before testing out this patch :-)
> 
> Throughput number of storage array is very from one product to another.
> On my hardware environment I think this number is valid and
> my patch is effective.

Hifumi-san, if you really want to merge, you should reproduce this
issue on typical hardware, I think.