Select and CPU Utlilization

[Tim Rotunda]

I am trying to understand Selects and how they effect system performance. Anyone care to comment on the following snipet of a glance screen?

Thanks,
Tim

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GLOBAL SYSTEM CALLS Users= 33
System Call Name ID Count Rate CPU Time Cum CPU
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fstat 92 679 133.1 0.00242 3.10617
select 93 157008 30785.8 0.56018 411.12575

[doug hosking]

Tim, before you dig too much on this, be sure you are current on kernel patches. You don't mention which HP-UX release, but, for example, for 11.00 patches PHKL_18543 and PHKL_27813 might be of interest in improving performance of select().

[rick jones]

regardless of just about anything else, it looks like this application is making a _VERY_ large number of calls to select() per second.

Probably worth some tusc tracing (verbose, enable lwpid logging) to see just what sort of select calls are being made.

if the select calls fit the sufficient pattern, a switch to eventports may be goodness - with the apropriate patches installed on 11 or 11i do a man 7 poll for more details.