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Subject: Re: [BENCHMARK] max bomb segment tuning with read latency 2 patch
	in  contest
From: GrandMasterLee <masterlee@digitalroadkill.net>
To: Andrew Morton <akpm@digeo.com>
Cc: Con Kolivas <conman@kolivas.net>,
       linux kernel mailing list <linux-kernel@vger.kernel.org>
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On Fri, 2002-12-06 at 23:55, Andrew Morton wrote:
[...]
> If the SMP machine is using scsi then that tends to make the elevator
> changes less effective.  Because the disk sort-of has its own internal
> elevator which in my testing on a Fujitsu disk has the same ill-advised
> design as the kernel's elevator: it treats reads and writes in a similar
> manner.
> 
> Setting the tag depth to zero helps heaps.
> 
> But as you're interested in `desktop responsiveness' you should be
> mostly testing against IDE disks.  Their behavour tends to be quite
> different.


One interesting thing about my current setup, with all scsi or FC disks,
is that bomb never displays > 0. 
Example: 

elvtune /dev/sdn yields:

/dev/sdn elevator ID            17
        read_latency:           8192
        write_latency:          16384
        max_bomb_segments:      0

elvtune -b 6 /dev/sdn yields:

/dev/sdn elevator ID            17
        read_latency:           8192
        write_latency:          16384
        max_bomb_segments:      0

Is it because I just do volume management at the hardware level and use
whole disks? Or is that something else?
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