Re: ocount fails with "too many open files"

Maynard Johnson <[email protected]>
Newsgroups gmane.linux.oprofile
Message-ID <[email protected]>
On 12/11/2014 03:32 PM, Henry May wrote:
> I'm running ocount on a P8 and getting this:
> 
> /usr/local/bin/ocount -b -e PM_RUN_CYC,PM_RUN_INST_CMPL,PM_DATA_FROM_L2MISS,PM_DATA_FROM_L2,PM_DATA_FROM_L3,PM_RC_LIFETIME_EXC_32,PM_RC_LIFETIME_EXC_256,PM_RC_LIFETIME_EXC_1024,PM_RC_LIFETIME_EXC_2048 -c -s -i 1000 -f /tmp/pmu_counts.csv
> Starting ocount Thu Dec 11 16:26:46 EST 2014
> Process ID: 154011
> perf_event_open failed with Too many open files
> Caught runtime error while setting up counters
> Internal Error.  Perf event setup failed.
> Error running ocount
> 
> If I reduce the number of counters, it works fine.  Also, I know I was running this same command successfully on a different P8 (now gone)
Henry,
Running ocount in --system-wide will result in a perf_event_open call being made for every CPU for each event, and each call returns a file descriptor.  I don't know exactly what kernel limit on open files is being exceeded here, but your best option is to do what you did -- reduce the number of events being counted.  Anyway, trying to count that many events at once, you're going to see a lot of multiplexing, which leads to scaling (i.e., basically guessing) what the total counts are.

-Maynard
> 
> 
> Henry May
> IBM InfoSphere Streams Performance
> [email protected]
> 720-342-8873
> Tie: 963-8873
> 
> 
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