Messages in this thread | | | Date | Wed, 25 Mar 2015 10:24:05 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] perf tool: Fix ppid for synthesized fork events |
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Em Wed, Mar 25, 2015 at 08:22:34AM -0400, Joe Mario escreveu: > On 03/24/2015 05:12 PM, David Ahern wrote: > >On 3/24/15 2:10 PM, Don Zickus wrote: > >>He does this with and without the patch. The difference is usually > >>over 50% extra time with the patch for both the record timings and > >>report timings.:-(
> >I find that shocking. The patch only populates ppid and ptid with a > >value read from the file that is already opened and processed. Most > >of the patch is just plumbing the value from the low level function > >that processes the status file back to synthesize_fork.
> >What benchmark is this? Is it something I can download and run? if so, details? site, command, args?
> Hi David:
> We ran "time perf mem record -a -e cpu/mem-loads,ldlat=50/pp -e > cpu/mem-stores/pp sleep 10" on a system that was running SPECjbb2013 > in the background. There were about 10,000 java threads with about > 500 to 800 in a runnable state at any given time. We ran it on a 4 > socket x86 IVB server.
So it starts when there are tons of threads in the system, for which synthezing from /proc will have to take place, without looking again at that patch, I can't think about what would be a problem :-\
> We had two perf binaries. One with your patch and one without it. > Because the benchmark doesn't always have a constant load, we ran the > above perf command in a loop alternating between the patched and > unpatched version. The elapsed wall clock times ("real" field from > time) for the perf with your patch was typically >= 50% longer than > the equivalent unpatched perf.
> We can't give out a copy of the SPEC benchmark (part of the SPEC > agreement). Try to find some application (or create your own) to load > the system with lots of busy threads.
Haven't tried, but head this is something that could perhaps be useful here:
http://kernel.ubuntu.com/~cking/stress-ng/
- Arnaldo
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