On 9/13/06, Jakob Oestergaard <[email protected]> wrote:
On Mon, Sep 11, 2006 at 04:00:32PM -0700, Dan Williams wrote:
> Neil,
>
...
>
> Concerning the context switching performance concerns raised at the
> previous release, I have observed the following. For the hardware
> accelerated case it appears that performance is always better with the
> work queue than without since it allows multiple stripes to be operated
> on simultaneously. I expect the same for an SMP platform, but so far my
> testing has been limited to IOPs. For a single-processor
> non-accelerated configuration I have not observed performance
> degradation with work queue support enabled, but in the Kconfig option
> help text I recommend disabling it (CONFIG_MD_RAID456_WORKQUEUE).
Out of curiosity; how does accelerated compare to non-accelerated?
One quick example:
4-disk SATA array rebuild on iop321 without acceleration - 'top'
reports md0_resync and md0_raid5 dueling for the CPU each at ~50%
utilization.
With acceleration - 'top' reports md0_resync cpu utilization at ~90%
with the rest split between md0_raid5 and md0_raid5_ops.
The sync speed reported by /proc/mdstat is ~40% higher in the accelerated case.
That being said, array resync is a special case, so your mileage may
vary with other applications.
I will put together some data from bonnie++, iozone, maybe contest,
and post it on SourceForge.
/ jakob
Dan
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