On 08/23/2009 06:48 AM, stephane eranian wrote: > Corey, > > On Sun, Aug 23, 2009 at 4:00 AM, Corey > Ashford<cjash...@linux.vnet.ibm.com> wrote: >> Hello, >> >> On Friday, we decided to double check that the recently checked-in changes >> for Power7 are working for perfmon2 (and perf_counters). >> > good idea. > >> So I set up a system with the latest 2.6.30 perfmon2 kernel, latest >> libpfm, and latest PAPI code. I ran the PAPI tests and immediately >> had a number of problems. >> >> The first problem is that there are missing groups in the power7_events.h >> file due to an error in the source file that I use >> to generate the C code. This can be corrected easily, and I will >> submit a patch later for it early next week. >> >> The second problem is that is that the mapping from PAPI events >> to native events required too many native events for PAPI_FP_OPS. >> This works OK for perf_counters, since it doesn't use the group >> tables to determine the values for the mmcr registers. However, >> the dispatch implementation in libpfm does use the groups, and there >> didn't exist a group containing all of the needed events. I can >> work around this by just removing one of the events so that a >> matching group can be found. We can probably generate a new >> group containing the needed event, and I will work on creating >> such a patch. (another solution would be to port the >> perf_counters code to libpfm, but that would be quite a lot >> of work) >> >> I left the worst for last: even running a simple test like >> libpfm/examples_v2.x/self, I get very inconsistent counts. >> Sometimes I get zeros! The numbers I get are almost always >> consistently less than they should be, which leads me to >> suspect that the pmd registers are getting zeroed out >> somewhere where they shouldn't be. >> >> I wasn't sure if this was due to some difference between Power7 >> and earlier chips, so I went and set up the same experiment >> on a Power5 machine, and the problem replicates there too. >> So this isn't a Power7-specific problem. Something changed >> between 2.6.29 and 2.6.30. When I run the same experiment on >> a perfmon2 2.6.29 kernel, the results are very consistent and >> look correct. >> >> I diffed the Power-specific source files that might have had some >> changes: >> arch/powerpc/perfmon/perfmon.c and >> arch/powerpc/perfmon/perfmon_power5.c >> but there are no differences between 2.6.29 and 2.6.30. >> > I don't see any major changes. > > Here are a couple of tests you could try and run to narrow it down: > - taskset -c 0 self > - syst > > Do those produce more stable and valid results? > >> Stephane, can you think of anything that you had to do in porting >> perfmon2 to 2.6.30 that might be causing this? >> > > Not enough data to figure it out. > >> Can you run examples_v2.x/self on x86 to see if you are seeing >> the same issue? >> > I did and it is stable and correct. So must be something in the > Power code or something in the generic code which impacts only > Power.
Thanks, Stephane. I'll look deeper into this issue tomorrow (work day). - Corey ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ perfmon2-devel mailing list perfmon2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
