lkml.org 
[lkml]   [2014]   [Feb]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/3] perf: fix synthesizing mmaps for threads
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


\
 
 \ /
  Last update: 2014-02-26 16:01    [W:0.345 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site