On Thu, Mar 16, 2017 at 11:54:58AM -0400, Vince Weaver wrote: > Hello > > My student actually noticed this before I did, I was hoping it was some > sort of error in her data. > > Anyway all perf_event functionality (especially reads) has become about > 20x slower, at least on Intel machines (haswell and skylake are the only > ones I've tested) sometime between 4.9 and 4.11-rc > > For example, in the PAPI tests: > > 4.11-rc2 > > Total cost for PAPI_read (2 counters) over 1000000 iterations > min cycles : 15192 > max cycles : 3887735 > mean cycles : 15662.057418 > std deviation: 19079.398693 > > > 4.9 > > Total cost for PAPI_read (2 counters) over 1000000 iterations > min cycles : 864 > max cycles : 78459 > mean cycles : 908.010315 > std deviation: 144.875697 > > > The perf_event_test validation tests are also showing this, even when > using rdpmc() rather than read. > > Is there a likely change that might have caused this? Hoping to avoid > bisecting it as that will kill the rest of the week probably.
No immediate clue; but I can have a poke. Do you have a handy way of showing this using: perf test rdpmc, or should I hack something together?
