linux-kernel - Re: async I/O seems to be blocking on 2.6.15

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Message-ID: <20061110092456.GO4527@kernel.dk>
Date:	Fri, 10 Nov 2006 10:24:57 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	"Chen, Kenneth W" <kenneth.w.chen@...el.com>
Cc:	Brent Baccala <cosine@...esoft.org>, linux-kernel@...r.kernel.org
Subject: Re: async I/O seems to be blocking on 2.6.15

On Mon, Nov 06 2006, Chen, Kenneth W wrote:
> I haven't done the measurement whether the time to submit I/O grows
> linearly with respect to I/O size.  Most likely it will.  If it is
> not, then we might have a scaling problem (though I don't believe we
> have this problem).

I would not expect it to, but ran a simple test to check submission
times from 32KiB to 2MiB:

Size		Time (usecs)
----------------------------
2MiB		223
1MiB		112
512KiB		 56
256KiB		 29
128KiB		 14
32KiB		  4

(note that I skipped 64KiB, things got boring). That clearly shows a
linear increase in time, so no scaling problem there.

-- 
Jens Axboe

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