Experimental Physics and
Industrial Control System

Mark Rivers <[email protected]> · Mon, 10 Sep 2012 21:58:55 +0000

Hi Lewis,

Thanks for the reply. 

I don't think that could be it, because I can reduce the CPU time of my application from 20% to 14% by changing a PV to eliminate calculations that are definitely done in my code.  I collected the profile with those calculations enabled, so at least (20-14)/20 = 30% of the CPU time should be in my calculation function.  It's spending the rest of its time reading short TCP messages which are coming in at 6.5 kHz, and I think that will result in a non-trivial amount of time in drvAsynIPPort.  Some of it will be in the system Ethernet driver, network stack, etc.

Thanks,
Mark

-----Original Message-----
From: J. Lewis Muir [mailto:[email protected]] 
Sent: Monday, September 10, 2012 4:49 PM
To: Mark Rivers
Cc: [email protected]
Subject: Re: How to profile an EPICS application on Linux

On 9/10/12 4:17 PM, Mark Rivers wrote:
> Does anyone with gprof experience know why I am not getting the execution times in these functions?

Hi, Mark.

I don't have gprof experience, but it could be that your
application is spending most of its time sleeping or blocking,
so, since gprof works by taking measurements while your
application is running in user-space, it sees time spent in your
application as very small compared to time spent in
kernel-space, and thus results in times rounded to 0 for all
those function calls.

The following article talks about this toward the end:

  http://www.ibm.com/developerworks/library/l-gnuprof.html

It suggests that if you run your application with the "time"
command and the output says you're spending hardly any time in
user-space, then gprof might not be useful to you.

Lewis

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System