On 02/22/2016 10:05 AM, Philip Mucci wrote: > HI Will, > > I’ve run into a problem with this on a Sandia system, where no matter how > hard I tried, I could not get libpfm to run. I had to hack libpfm enough to > get it to use the internal systems perf_event.h… I haven’t tried it recently, > to see if everything started working again. My approach however is bogus > overall, because the idea of libpfm currently is to use the most recent > header file we have and zero everything out. (I think it was the evil > exclude_guest plus paranoid=1 combo that did it). The kernel seems to do a > good job of ignoring everything extra as far as I can tell… So I’ve never yet > had an issue with writing zeroes everywhere in a big struct and handing it to > old kernels…. > > One thing we did have a request come in is that we have REAL shared library > versioning so if you have a patch for this, that would be great. Major > version should signify API breakage…. > > Regards
Hi Phil, I just started recently using libabigail to look for these types of problems. I haven't taken a look at the linux perf or the data struct that it passes to the kernel. Do you recall which versions of kernels and libpfm were being used? It might be useful to check that with abidiff. libpfm does set the soname to mark libpfm3 different from libpfm4. However, there is room for improvement, hiding internal functions and data structures. One of the problems I see with defining an abi version for libpfm is how does the addition of new processor implementations count? Is that considered an (minor) abi change? Not an abi change at all? There are pfm_pmu_t in pfmlib.h that change with the addition of new processors. -Will > >> On Feb 17, 2016, at 10:27 PM, William Cohen <wco...@redhat.com> wrote: >> >> One thing that is concerning is the change to perf_event_attr_t for >> pfm_get_perf_event_encoding. The struct is now larger. This could >> lead to some fields being uninitialized when passed into a libpfm >> function or could cause writes pass the end of smaller sized struct >> used in older code. > ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 _______________________________________________ perfmon2-devel mailing list perfmon2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
