Re: Async Pages and Thread Pools

Hi Chris,

The following article also show you some benefits and results of using Asyc
page. One thing I think good there is it also mentioned what you need to
take care when determine to use async page. That's whether the operation
you want to run in async page is executing on a custom thread rather than
thread-pool thread. If the task itself also ocuppy thread-pool thread,
async page won't help much:

#Async Pages in ASP.NET 2.0 - some results
http://www.pluralsight.com/blogs/fritz/archive/2004/10/19/2892.aspx

You can also get more info about ASP.NET threading model through the
following webcast materials:

#Support WebCast: Microsoft ASP.NET Threading
http://support.microsoft.com/kb/820913

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead



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--------------------
From: "Chris Marsh" <cjmarsh@xxxxxxxxxxxxxxxx>
References: <OKjj3GkaIHA.4180@xxxxxxxxxxxxxxxxxxxx>
<ux9hP0kaIHA.536@xxxxxxxxxxxxxxxxxxxx>
Subject: Re: Async Pages and Thread Pools
Date: Fri, 8 Feb 2008 14:04:19 -0000

Kevin

Many thanks for the response.

"Kevin Spencer" <unclechutney@localhost> wrote in message
news:ux9hP0kaIHA.536@xxxxxxxxxxxxxxxxxxxxxxx
The advantage of Asynch ASP.Net pages is seen when the number of
concurrent requests exceeds the number of available request-processing
threads in the thread pool. The size of the thread pool is limited, and
if
exceeded, successive requests can be delayed, or if there are enough
requests, some may eventually time out waiting for a thread, resulting
in
a "503 Server Unavailable" error from the server. Asynch ASP.Net pages
return the request-processing thread to the thread pool immediately,
using
another thread to do the actual processing. When the processing is
completed, another request-processing thread is grabbed to return the
Response to the client.

So, if we have an IIS thread pool size of 25 and 25 requests are made that
involve intensive IO, other requests (for inexpensive resources that
*should* be served very quickly) will not be served until at least one of
the other threads is freed up. If we use asynchronous page processing, we
hand off processing of the intensive IO operations to threads outside the
IIS thread pool, thus freeing up threads from the IIS thread pool to
service
other requests.

What I don't understand is what benefit using asynchronous page processing
has over simply increasing the number of threads in the IIS thread pool.
Why
does it matter whether threads are taken from the IIS thread pool or not?

[..]

http://msdn.microsoft.com/msdnmag/issues/05/10/WickedCode/

A useful resource, thanks.

--
Regards

Chris Marsh




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