Skip site navigation (1) Skip section navigation (2)

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: 438BE53B.1090106@boreham.org (view raw or flat)
Thread:
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
>>'pre-fetching'.
>>    
>>
>
>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.



In response to

Responses

pgsql-hackers by date

Next:From: Gavin SherryDate: 2005-11-29 05:25:17
Subject: Re: ice-broker scan thread
Previous:From: Qingqing ZhouDate: 2005-11-29 05:09:11
Subject: Re: ice-broker scan thread

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group