[THIN] Re: Full desktop for 900 users

  • From: "Braebaum, Neil" <neil.braebaum@xxxxxxxxxxxxxxxxxxxxxxxx>
  • To: "'thin@xxxxxxxxxxxxx'" <thin@xxxxxxxxxxxxx>
  • Date: Wed, 27 Nov 2002 16:50:37 -0000

Comments inline...

> -----Original Message-----
> From: Bernd Harzog [mailto:Bernd.Harzog@xxxxxxxxxxx] 
> Sent: 27 November 2002 16:38
> To: thin@xxxxxxxxxxxxx
> Subject: [THIN] Re: Full desktop for 900 users
> 
> Neil,
> 
> I have no doubt that you could configure Perfmon to measure 
> Kernel Mode activity. My point was that the commonly used CPU 
> utilization counters like the CPU one in Task Manager do not 
> fully account for things going in the OS.

Again task manager will track kernel activity, if you ask it to.

> We know this 
> because we have seen TScale optimize applications on servers, 
> reduce page file (kernel mode activity), and then see CPU 
> utilization go UP.

Isn't this slightly expected, though?

(I'll elaborate after the next bit...)

> This is because some kernel time which was 
> blocking user time went away,

Is it? Or merely that kernel activity that would have required either more
of, or slower operations (ie pagefile access) would take longer?

> and the CPU was now more 
> available to do useful work for users.

If you either take something slow away like this, you'd expect the cpu to be
able to do more, and to actually do more - because it's hasn't got to spend
so much time waiting.

Don't forget though, that normal physical memory access will be kernel
activity (or at least a component of it will be).

However, in the scenario to which you allude - effectively less demand for
paging, therefore less *slow* access (kernel wait times) - you have higher
cpu activity observable because if a higher *rate* of context switches as
it's doing more active work with it's timeslices.

None of which means, nor implies, that either taskmanager, nor perfmon are
misleading - dont' forget, they normally chart activity WRT time.

Neil

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