Messages in this thread Patch in this message | | | From | Don Zickus <> | Subject | [PATCH] perf: Fallback to MAP__FUNCTION if daddr maps are NULL | Date | Wed, 20 Aug 2014 23:25:11 -0400 |
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As we run "perf c2c" on more applications, we noticed we're missing significant samples from a common customer's application. Looking at the /proc/<pid>/maps file for the app, we see "rwxs" and "rwxp" permissions on many of the shared memory & heap regions, and on all the thread stacks.
Because those regions have the "x" bit set, perf marks them with a MAP_FUNCTION type. Hence ip_resolve_data() never finds load or store events coming from them.
We fixed this by re-calling thread__find_addr_location with MAP__FUNCTION in the case where map is NULL as a last ditch effort to map the sample before giving up and dropping it.
Reported-by: Joe Mario <jmario@redhat.com> Tested-by: Joe Mario <jmario@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> --- tools/perf/util/machine.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-)
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index 0e5fea9..e62bd87 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -1241,6 +1241,16 @@ static void ip__resolve_data(struct machine *machine, struct thread *thread, thread__find_addr_location(thread, machine, m, MAP__VARIABLE, addr, &al); + if (al.map == NULL) { + /* + * some shared data regions have execute bit set which puts + * their mapping in the MAP__FUNCTION type array. + * Check there as a fallback option before dropping the sample. + */ + thread__find_addr_location(thread, machine, m, MAP__FUNCTION, addr, + &al); + } + ams->addr = addr; ams->al_addr = al.addr; ams->sym = al.sym; -- 1.7.1
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