Messages in this thread | | | Date | Wed, 13 Sep 2006 12:17:55 -0700 | From | "Dan Williams" <> | Subject | Re: [PATCH 00/19] Hardware Accelerated MD RAID5: Introduction |
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On 9/13/06, Jakob Oestergaard <jakob@unthought.net> 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
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