There is a similar patch (in google branches) from Rong Xu which enables atomic profile counter update.
http://gcc.gnu.org/ml/gcc-patches/2013-01/msg00072.html On Mon, Apr 22, 2013 at 12:59 PM, Bill Schmidt <wschm...@linux.vnet.ibm.com> wrote: > Six years ago, Michael Matz proposed a patch for generating profile > instrumentation in a thread-safe manner: > > http://gcc.gnu.org/ml/gcc-patches/2007-03/msg00950.html > > Reading through the thread, I saw a few minor objections, but nothing to > indicate the patch should be withdrawn. However, apparently the changes > were never made. > > I'm curious about the history here. What was the reason for abandoning > this? Was a better alternative found? Were all the counters made > thread-local? > > My reason for asking involves a large heavily-threaded application that > is improved by feedback-directed optimization on some platforms, but not > on others. One theory is that a defective profile is generated due to > counter dropouts from contention. I'm somewhat skeptical about this > given that some platforms seem to do well with it, but it's possible. Do you see lots of messages about insane profile data (under -fprofile-correction)? Most of the such messages we see (in our large multi-threaded applications) show only marginal errors. > I'm hopeful that knowing why the thread-safe profiling patch wasn't > implemented will give us more of a clue. You can try out Rong's patch. He plan to submit it to trunk soon. thanks, David > > Thanks for any help! > > Bill >
