Messages in this thread | | | Date | Tue, 22 Apr 2014 15:40:31 -0400 | From | Don Zickus <> | Subject | Re: [PATCH] perf tools: fix processing of pid/tid for mmap records |
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On Mon, Apr 21, 2014 at 06:06:55PM +0200, Stephane Eranian wrote: > perf tools: fix processing of pid/tid for mmap records > > Mmaps are global to a process (always). Processing them > per-thread was causing some serious issues in case mmaps > would overlap. The overlap fixups would only occur in the > context of the thread which generated the overlapping > mmap. But that was cause issues later on when a sample > from another thread would fall into that overlapping > mmap.
eh? You are basically reverting my patch for a similar problem. :-)
I was running a large multi-threading program (specjbb) and the threads were not being seperated into their own map'd areas. So either I had to lump all threads in to the same pid space or make the change you are reverting.
The problem I had with the double pid (as you propose), I would later look up samples based on pid/tid and there would be _no_ map available because it was created as a pid/pid pair. As a result, our c2c program would drop thousands of samples on the floor (because there was no mapping for the data address to get the major/minor/inode info).
Now I modified our c2c program to lookup samples as pid/pid but now the maps lost tid info, and I had to hack around that by carrying the tid info in a private struct.
Hopefully Jiri's thread work using pointers will solve both our problems. :-) But I can't ack your patch because it will break my work :-(
Cheers, Don
> > The solution to the problem is to handle ALL mmaps as > occurring in the master thread (pid = tid) and then to > lookup for thread map using pid as the tid argument. > This is how samples are looking up for the thread map > already (notice pid passed twice): > > int perf_event__preprocess_sample(const union perf_event *event, > struct machine *machine, > struct addr_location *al, > struct perf_sample *sample) > { > struct thread *thread = machine__findnew_thread(machine, sample->pid, > sample->pid); > } > > Without this fix, some samples in overlapping regions > may not be symbolized. > > Signed-off-by: Stephane Eranian <eranian@google.com> > > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c > index a53cd0b..43cdc0a 100644 > --- a/tools/perf/util/machine.c > +++ b/tools/perf/util/machine.c > @@ -1025,9 +1025,9 @@ int machine__process_mmap2_event(struct machine *machine, > goto out_problem; > return 0; > } > - > + /* only look by pid for mmap events */ > thread = machine__findnew_thread(machine, event->mmap2.pid, > - event->mmap2.tid); > + event->mmap2.pid); > if (thread == NULL) > goto out_problem; > > @@ -1073,9 +1073,9 @@ int machine__process_mmap_event(struct machine *machine, union perf_event *event > goto out_problem; > return 0; > } > - > + /* only look by pid for mmap events */ > thread = machine__findnew_thread(machine, event->mmap.pid, > - event->mmap.tid); > + event->mmap.pid); > if (thread == NULL) > goto out_problem; > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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