Messages in this thread | | | Date | Wed, 26 Feb 2014 11:32:08 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 3/3] perf: fix synthesizing mmaps for threads |
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Em Wed, Feb 26, 2014 at 11:17:26AM -0300, Arnaldo Carvalho de Melo escreveu: > Em Tue, Feb 25, 2014 at 10:43:47PM -0500, Don Zickus escreveu: > > Currently if a process creates a bunch of threads using pthread_create > > and then perf is run in system_wide mode, the mmaps for those threads > > are not captured with a synthesized mmap event. > > > > The reason is those threads are not visible when walking the /proc/ > > directory looking for /proc/<pid>/maps files. Instead they are discovered > > using the /proc/<pid>/tasks file (which the synthesized comm event uses). > > > > This causes problems when a program is trying to map a data address to a > > tid. Because the tid has no maps, the event is dropped. Changing the program > > to look up using the pid instead of the tid, finds the correct maps but creates > > ugly hacks in the program to carry the correct tid around. > > > > Fix this by synthesizing mmap events for each tid found in the /proc/<pid>/tasks > > file. > > This seems to cover two problems, the first is for mmap/mmap2 event > processing to lookup pid/tid instead of pid/pid, the other one is to > iterate thru /proc/pid/tasks/, so this needes spliting up. > > Now looking at the /tasks/ part...
Agreed we need to synthesize the mmap events for the threads in /proc/pid/task/, but that need to be done in perf_event__synthesize_mmap_events, not in perf_event__synthesize_comm_events, that should remain just for synthesizing comm events .
I.e. we should move that /tasks/ traversal from synthesize_comm to its caller and from there synthesize the mmaps too.
I can do that if you don't beat me to it. :-)
- Arnaldo
> > This may not be entirely clean but it seems to work. > > > > Signed-off-by: Don Zickus <dzickus@redhat.com> > > --- > > tools/perf/util/event.c | 15 +++++++++++---- > > tools/perf/util/machine.c | 4 ++-- > > 2 files changed, 13 insertions(+), 6 deletions(-) > > > > diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c > > index 086c7c8..09c53bb 100644 > > --- a/tools/perf/util/event.c > > +++ b/tools/perf/util/event.c > > @@ -93,10 +93,13 @@ static pid_t perf_event__get_comm_tgid(pid_t pid, char *comm, size_t len) > > } > > > > static pid_t perf_event__synthesize_comm(struct perf_tool *tool, > > - union perf_event *event, pid_t pid, > > + union perf_event *event, > > + union perf_event *mmap_event, > > + pid_t pid, > > int full, > > perf_event__handler_t process, > > - struct machine *machine) > > + struct machine *machine, > > + bool mmap_data) > > { > > char filename[PATH_MAX]; > > size_t size; > > @@ -168,6 +171,10 @@ static pid_t perf_event__synthesize_comm(struct perf_tool *tool, > > tgid = -1; > > break; > > } > > + > > + /* process the thread's maps too */ > > + perf_event__synthesize_mmap_events(tool, mmap_event, pid, tgid, > > + process, machine, mmap_data); > > } > > > > closedir(tasks); > > @@ -331,8 +338,8 @@ static int __event__synthesize_thread(union perf_event *comm_event, > > struct perf_tool *tool, > > struct machine *machine, bool mmap_data) > > { > > - pid_t tgid = perf_event__synthesize_comm(tool, comm_event, pid, full, > > - process, machine); > > + pid_t tgid = perf_event__synthesize_comm(tool, comm_event, mmap_event, pid, > > + full, process, machine, mmap_data); > > if (tgid == -1) > > return -1; > > return perf_event__synthesize_mmap_events(tool, mmap_event, pid, tgid, > > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c > > index 813e94e..eb26544 100644 > > --- a/tools/perf/util/machine.c > > +++ b/tools/perf/util/machine.c > > @@ -1026,7 +1026,7 @@ int machine__process_mmap2_event(struct machine *machine, > > } > > > > thread = machine__findnew_thread(machine, event->mmap2.pid, > > - event->mmap2.pid); > > + event->mmap2.tid); > > if (thread == NULL) > > goto out_problem; > > > > @@ -1074,7 +1074,7 @@ int machine__process_mmap_event(struct machine *machine, union perf_event *event > > } > > > > thread = machine__findnew_thread(machine, event->mmap.pid, > > - event->mmap.pid); > > + event->mmap.tid); > > if (thread == NULL) > > goto out_problem; > > > > -- > > 1.7.11.7
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