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SubjectRe: [PATCH] perf: Don't clone maps from parent when synthesizing forks
Em Wed, Oct 31, 2018 at 02:01:38PM +0100, Jiri Olsa escreveu:
> On Tue, Oct 30, 2018 at 10:24:04PM -0700, David Miller wrote:
>
> SNIP
>
> > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> > index 111ae858cbcb..214b7979c4e7 100644
> > --- a/tools/perf/util/machine.c
> > +++ b/tools/perf/util/machine.c
> > @@ -1708,6 +1708,7 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
> > struct thread *parent = machine__findnew_thread(machine,
> > event->fork.ppid,
> > event->fork.ptid);
> > + bool do_maps_clone = true;
> > int err = 0;
> >
> > if (dump_trace)
> > @@ -1737,8 +1738,11 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
> > thread = machine__findnew_thread(machine, event->fork.pid,
> > event->fork.tid);
> >
> > + if (event->fork.header.misc & PERF_RECORD_MISC_FORK_EXEC)
> > + do_maps_clone = false;
>
> could you please put some comment in here shortly
> explaining the reason behind this flag

I'll get that comment from the commit log message

> > +
> > if (thread == NULL || parent == NULL ||
> > - thread__fork(thread, parent, sample->time) < 0) {
> > + thread__fork(thread, parent, sample->time, do_maps_clone) < 0) {
> > dump_printf("problem processing PERF_RECORD_FORK, skipping event.\n");
> > err = -1;
> > }
> > diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
> > index 2048d393ece6..54b2c9ceba9f 100644
> > --- a/tools/perf/util/thread.c
> > +++ b/tools/perf/util/thread.c
> > @@ -330,7 +330,8 @@ static int thread__prepare_access(struct thread *thread)
> > }
> >
> > static int thread__clone_map_groups(struct thread *thread,
> > - struct thread *parent)
> > + struct thread *parent,
> > + bool do_maps_clone)
> > {
> > /* This is new thread, we share map groups for process. */
> > if (thread->pid_ == parent->pid_)
> > @@ -341,15 +342,14 @@ static int thread__clone_map_groups(struct thread *thread,
> > thread->pid_, thread->tid, parent->pid_, parent->tid);
> > return 0;
> > }
> > -
> > /* But this one is new process, copy maps. */
> > - if (map_groups__clone(thread, parent->mg) < 0)
> > + if (do_maps_clone &&
> > + map_groups__clone(thread, parent->mg) < 0)
> > return -ENOMEM;
> > -
> > return 0;
>
> we could move all this into one line:
>
> return do_maps_clone ? map_groups__clone(thread, parent->mg) : 0;

Yeah, I can do that as well, after looking at what map_groups__clone()
returns, which can go into the unwind backends.

- Arnaldo

> thanks,
> jirka
>
> > }
> >
> > -int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
> > +int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone)
> > {
> > if (parent->comm_set) {
> > const char *comm = thread__comm_str(parent);
> > @@ -362,7 +362,7 @@ int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
> > }
> >
> > thread->ppid = parent->tid;
> > - return thread__clone_map_groups(thread, parent);
> > + return thread__clone_map_groups(thread, parent, do_maps_clone);
> > }
> >
> > void thread__find_cpumode_addr_location(struct thread *thread, u64 addr,
> > diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
> > index 07606aa6998d..7e30fe99b74b 100644
> > --- a/tools/perf/util/thread.h
> > +++ b/tools/perf/util/thread.h
> > @@ -87,7 +87,7 @@ struct comm *thread__comm(const struct thread *thread);
> > struct comm *thread__exec_comm(const struct thread *thread);
> > const char *thread__comm_str(const struct thread *thread);
> > int thread__insert_map(struct thread *thread, struct map *map);
> > -int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp);
> > +int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone);
> > size_t thread__fprintf(struct thread *thread, FILE *fp);
> >
> > struct thread *thread__main_thread(struct machine *machine, struct thread *thread);

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