Re: CFQ iosched praise: good perfomance and better latency

From: Nick Piggin
Date: Mon Apr 19 2004 - 06:54:45 EST

Pedro Larroy wrote:
On Mon, Apr 19, 2004 at 04:12:56PM +1000, Nick Piggin wrote:

Well I think Pedro actually means *seconds*, not ms. The URL
shows AS peaks at nearly 10 seconds latency, and CFQ over 2s.

Yes, I meant seconds, my mistake. I will be testing elevator=noop this

That would be interesting.

It really seems like a raid problem though, because latency
measured at the individual devices is under 250ms for AS.

Probably. But I was surprised to find that bonnie gave similar results
with CFQ and with AS when benchmarking the swraid5.

I haven't used bonnie, but I think it is single threaded, isn't
it? If that is the case, then the IO scheduler will make little
or no difference, so your result is not surprising.
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