RE: How to profile an EPICS application on Linux

[Mark Rivers <rivers@cars.uchicago.edu>]

Here is the output of "time" when running it in a mode where "top" showed the application using about 95% of a single CPU (on a 16 core system).  This is with my calculations enabled.

23.547u 16.516s 0:52.39 76.4%   0+0k 0+24io 0pf+0w

This is the output of time when the calculations are disabled and top shows about 80% CPU in my application.

Disabling my calculations:
11.401u 8.008s 0:27.60 70.2%    0+0k 0+8io 0pf+0w

So it spends a substantial amount of CPU time in both User Mode and Kernel Mode.

Mark


-----Original Message-----
From: J. Lewis Muir [mailto:jlmuir@imca-cat.org] 
Sent: Monday, September 10, 2012 5:03 PM
To: Mark Rivers
Cc: tech-talk@aps.anl.gov
Subject: Re: How to profile an EPICS application on Linux

On 9/10/12 4:58 PM, Mark Rivers wrote:
> 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.

Hi, Mark.

What does the "time" command show?

Lewis