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SubjectRe: [PATCH] dcache: Translating dentry into pathname without taking rename_lock
On 09/04/2013 04:40 PM, John Stoffel wrote:
>>>>>> "Waiman" == Waiman Long<waiman.long@hp.com> writes:
> Waiman> In term of AIM7 performance, this patch has a performance boost of
> Waiman> about 6-7% on top of Linus' lockref patch on a 8-socket 80-core DL980.
>
> Waiman> User Range | 10-100 | 200-10000 | 1100-2000 |
> Waiman> Mean JPM w/o patch | 4,365,114 | 7,211,115 | 6,964,439 |
> Waiman> Mean JPM with patch | 3,872,850 | 7,655,958 | 7,422,598 |
> Waiman> % Change | -11.3% | +6.2% | +6.6% |
>
> This -11% impact is worisome to me, because at smaller numbers of
> users, I would still expect the performance to go up. So why the big
> drop?
>
> Also, how is the impact of these changes on smaller 1 socket, 4 core
> systems? Just because it helps a couple of big boxes, doesn't mean it
> won't hurt the more common small case.
>
> John

I don't believe the patch will make it slower with less user. It is more
a result of run-to-run variation. The short workload typically completed
in a very short time. In the 10-100 user range, the completion times
range from 0.02-0.11s. With a higher user count, it needs several
seconds to run and hence the results are more reliable.

Longman


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