Re: IIS6 APS Thread Use

From: Egbert Nierop \(MVP for IIS\) (egbert_nierop_at_nospam.invalid)
Date: 02/01/05 

Date: Tue, 1 Feb 2005 09:51:48 +0100

"AIMTech" <AIMTech@newsgroups.nospam> wrote in message
news:OWzbc97BFHA.2380@tk2msftngp13.phx.gbl...
> Thanks for the reply.
>
> For testing IIS6 is configured to have 20 ASP threads and MACT is
> configured
> to have 50 concurrent users.
>
> The COM application *is* multi-threaded - I was giving an extreme example
> with it settling on using a single thread. With 50 concurrent users the
> number of ASP threads in use can be between 1 and all 20 but it tends to
> use
> the lower number.
> I just don't understand why, if there are threads available to IIS why it
> does not use them?

Because MS has made IIS optimized between resources (threads) and
scalability (the max no of users vs throughput).
In a multithreaded system, simply allocating 100 threads per CPU in the ASP
Thread pool, would cause a lot heavy thread context switching.

> Thanks
> ----------------------------------------------------------------------------
> ----------
>
> "Egbert Nierop (MVP for IIS)" <egbert_nierop@nospam.invalid> wrote in
> message news:#brX6ajBFHA.2600@TK2MSFTNGP09.phx.gbl...
>> "AIMTech" <AIMTech@newsgroups.nospam> wrote in message
>> news:u5CwKoiBFHA.2392@TK2MSFTNGP14.phx.gbl...
>> > Is there an explanation somewhere as to how IIS6 determins how many ASP
>> > threads its actually going to use?
>> >
>> > I have configured IIS6 to have 20 threads (ASPProcessorThreadMAX) but
>> > it
>> > rarely uses them all.
>> >
>> > I am using the MACT test tool to stress test and with 50 concurrent
> users
>> > I
>> > quite often see only a single ASP thread being used the other 49 are on
>> > the
>> > Requests Queued. The Request Wait Time in Perfmon can be averaging
> around
>> > 5
>> > or 6 seconds and there is plenty of spare CPU.
>>
>> using MACT, do you also enable 20 users (connections)?
>> Do you use COM objects such as VB6 which you put in the application or in
>> the session? If yes, that's the reason that IIS turns to single threading
>> (as if). It needs to marshale and synchronize.
>>
>>
>> --
>> compatible web farm Session replacement for Asp and Asp.Net
>> http://www.nieropwebconsult.nl/asp_session_manager.htm
>>
>>
>> > The application quite often has long running queries (15 to 20 seconds
> per
>> > request) and rather than use another thread IIS will quite often just
> keep
>> > ticking along with the threads its using with the result that the
> Request
>> > Wait Time can jump significantly.
>> >
>> >
>> >
>> >
>>
>
>

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