Messages in this thread | | | Date | Mon, 21 Nov 2011 11:05:29 -0500 | From | William Cohen <> | Subject | Re: [RFC][PATCH 0/6] perf: x86 RDPMC and RDTSC support |
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On 11/21/2011 10:02 AM, Vince Weaver wrote: > On Mon, 21 Nov 2011, Peter Zijlstra wrote: > >> These few patches implement x86 RDPMC support and add an extention to the self >> monitoring data to also allow additional time updates using userspace TSC reads. >> >> There's a few loose ends, but it mostly seems to work. > > I'll have to test these out. > > I have some low-level benchmarks I've been working on, you can see some > preliminary results here: > http://web.eecs.utk.edu/~vweaver1/projects/perf-events/benchmarks/ > > perf_events was lagging behind perfmon2 and perfctr in self-monitoring > overhead, but maybe these changes will help that. > > perf_event overhead got a lot worse between 2.6.32 and 3.0, I'm mid-bisect > on that trying to isolate the cause. > > Vince >
Hi Vince,
Any improvements in performance of self-monitoring would be welcomed. International Symposium on computer Architecture (ISCA 2011) has paper about a low overhead mechanism to read out the performance counters, LiMiT (http://castl.cs.columbia.edu/limit/index.php/LiMiT) that avoids using system calls to read the performance counter data. That paper shows a fair amount of overhead for PAPI.
-Will
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