Message-ID: <4083BDBB.2050904@yahoo.com.au>
Date: Mon, 19 Apr 2004 21:53:31 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Pedro Larroy <piotr@larroy.com>
CC: Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: CFQ iosched praise: good perfomance and better latency
References: <20040419005651.GA7860@larroy.com> <40835F4E.5000308@yahoo.com.au> <20040418225752.56d10695.akpm@osdl.org> <40836DE8.5080303@yahoo.com.au> <20040419113243.GA18042@larroy.com>
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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
> evening.
> 

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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