Re[2]: WinVNC & NT: 100% CPU utilization Shane_McLaughlin "at"
Wed, 25 Mar 1998 12:44:28 +0000

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     Don't forget that the taskmanager itself is notorious for hogging a 
     lot of resources - typical M$ bloatware - i *think* that may be fixed 
     in a service pack update (a.k.a. bugfix)
     try ps.exe, a port of the unix ps command to win32.
     There's a lot of versions floating around on the 'Net,
     I recommend the Cygnus GNU-Win32 port of the GNU Un*x GCC, + unix 
     shell utils.
     great for Unix junkies stuck with a win32 machine
     This should have a lot less resource usage. 16MB for the entire development 
     Drop me a line and i'll email you ps.exe and the necessary cygwin.dll 
     to run it. As well, the individual files are also buried deeply on 
     Cygnus' FTP site.

______________________________ Reply Separator _________________________________
Subject: Re: WinVNC & NT: 100% CPU utilization
Author:  "James [Wez] Weatherall" <jnw "at"> at Internet
Date:    3/25/98 10:21 AM

On Tue, 24 Mar 1998, dave w capella wrote:
> I fired up the NT's TaskMgr to monitor CPU & memory use. To my 
> surprise, I found that with only WinVNC running, serving 2 clients,
> my CPU utilization hit the ceiling (100%). It's only got 32mb, but only 
> 28mb were committed (no thrashing). A check of all processes
> revealed that WinVNC was taking 85% - 98% of the CPU's time. The only 
> other processes running were the standard NT server services: IIS,FTP, 
> standard TCP services.
Connecting multiple clients to WinVNC is known to increase CPU usage. 
However, under Windows NT this should rarely prove to be a problem, since 
WinVNC will be scheduled in the same way as any other user application and 
so will not lock out other processes.
Note also that WinVNC's CPU usage will rise proportionally to the area of 
the screen being updated.  This means that dragging large windows, or 
having large windows regularly updating (e.g. the system clock maxmised to 
fill the screen), will cause CPU usage to peak.
However, I suspect the real reason for this apparent performance hit is 
that you're running the Task Manager on the desktop of an NT box that is 
being viewed by two VNC clients.  So a large proportion of the CPU cycles 
being used by WinVNC will be coming from the fact that you have the Task 
Manager updating it's display every half second or so, to two clients.  I 
managed to get roughly the CPU usage you describe (although I have two 
CPU's, so I was looking for only ~40% usage on average, as being 
comparable).  When I close the task manager, CPU usage drops markedly.
> I've been telling colleagues that this is *not* resource hungry, and 
> I could have sworn that my earlier tests bore this out. Any idea why 
> this 'virgin' machine would exhibit such behavior? Or were my earlier 
> results wrong?
Were you performing similar tasks in your original trials to the case 
described above?  How many clients did you originally have connected?
James "Wez" Weatherall
Olivetti & Oracle Research Laboratory, Cambridge, UK. 
Tel : Work - 343000
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From: "James [Wez] Weatherall" <jnw "at">
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Subject: Re: WinVNC & NT: 100% CPU utilization
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