Re: Issue with AHCI driver

[Tejun Heo <tj@kernel.org>]

the4hoffmans@earthlink.net wrote:
> Sorry about the multiple e-mails Jeff, but our IT group has seen fit
> to deny me the ability to send e-mail to vger.kernel.org so I'm
> trying again from my own personal account. 
> -------------------------------------------------------------------
> 
> 
> My name is Bob Hoffman.  I am a software engineer for Micron
> Technology in Minneapolis.  I have been working on AHCI drivers.  We
> recently installed kernel build 2.6.19.0 (unpatched) of Linux on an
> Intel motherboard system which includes the ICH9 SATA controller.  We
> have been running some benchmarks and found that the SATA harddrives
> looked slow.  When I attached a SATA analyzer it shows that we are
> only getting one command "in flight" or "outstanding" at a time, and
> it is always slot (or tag) zero.  The AHCI driver doesn't seem to be
> taking advantage of the 32 deep queue.
> 
> I checked the queue depth using the info at
> http://linux-ata.org/faq.html#io32 and it shows "NCQ (depth 31/32)".
> I'm wondering if there is something else I need to know.
> 
> I've copied our "Linux guru", Bob Ward, who knows more about the
> kernel stuff than I do.
> 
> Thank you for any help you can provide. Bob (Hoffman) ; ) -- To
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What kind of workload are you testing?  If you're doing multiple random
IOs, using deadline io scheduler will give you a better result.  Can't
say whether that would help on any realistic workload tho.

-- 
tejun