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Re: ice-broker scan thread

From: David Boreham <david_list(at)boreham(dot)org>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: ice-broker scan thread
Date: 2005-11-29 05:20:59
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Qingqing Zhou wrote:

>On Mon, 28 Nov 2005, Gavin Sherry wrote:
>>MySQL, Oracle and others implement read-ahead threads to simulate async IO
>Due to my tests on Windows (using the attached program and change
>enable_aio=true), seems aio doesn't help as a separate thread - but maybe
>because my usage is wrong ...
I don't think your NT overlapped I/O code is quite right. At least
I think it will issue reads at a high rate without waiting for any of them
to complete. Beyond some point that has to give the kernel gut-rot.
But anyway, I wouldn't expect the use of aio to make any
significant difference in an already threaded test program.
The point of aio is to allow
I/O concurrency _without_ the use of threads or multiple processes.
You could re-write your program to have a single thread but use aio.
In that case it should show the same read ahead benefit that you see
with the thread.

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Subject: Re: ice-broker scan thread
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