Asai Thambi S P [off-list ref] writes:

On 6/1/2011 2:21 PM, Alan Cox wrote:

quoted

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Thanks, Asai!  I don't think cfq is the ideal I/O scheduler to be
testing.  Could you run again with deadline and/or noop and see how that
changes your throughput and perf report?  Also, just for completeness,
could you tell us which kernel you ran this against?

kernel 2.6.38.6

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How many processors is this system, just looking at the lock contention
which is pretty horrible.

8 processors (2 quad-core CPUs)
Intel(R) Xeon(R) CPU           X5672  @ 3.20GHz

[...]

On looking into the data in below links, lock and block queue are
consuming more time when running with ahci driver. Correct me if I
missing something.

2.6.39 introduced the on-stack plugging work from Jens, the intent of
which is to reduce queue lock contention.  It would be great if you
could run with that kernel and noop to see if we make up some of the
performance gap (which looks to be just north of 10%).

Asai, thanks for running these tests and providing all of this data!

-Jeff