Messages in this thread | | | Date | Fri, 09 Dec 2011 10:08:19 -0700 | From | David Ahern <> | Subject | Re: [PATCH] perf: fix comm for processes with named threads |
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Disregard. Need to update to your latest core branch.
On 12/09/2011 09:00 AM, David Ahern wrote: > perf does not properly handle monitoring of processes with named threads. > For example: > > $ ps -C myapp -L > PID LWP TTY TIME CMD > 25118 25118 ? 00:00:00 myapp > 25118 25119 ? 00:00:00 myapp:worker > > perf record -e cs -c 1 -fo /tmp/perf.data -p 25118 -- sleep 10 > perf report --stdio -i /tmp/perf.data > 100.00% myapp:worker [kernel.kallsyms] [k] perf_event_task_sched_out > > The process name is set to the name of the last thread it finds for the > process. > > The Problem: > perf-top and perf-record both create a thread_map of threads to be > monitored. That map is used in perf_event__synthesize_thread_map which > loops over the entries in thread_map and calls __event__synthesize_thread > to generate COMM and MMAP events. > > __event__synthesize_thread calls perf_event__synthesize_comm which opens > /proc/pid/status, reads the name of the task and its thread group id. > That's all fine. The problem is that it then reads /proc/pid/task and > generates COMM events for each task it finds - but using the name found > in /proc/pid/status where pid is the thread of interest. This means the > name of the last thread processed sets the name for all threads in the > process - which is not good for multithreaded processes with named > threads. > > The Fix: > perf_event__synthesize_comm has an input argument (full) that decides > whether to process task entries for each pid it is passed. It currently > never set to 0 (perf_event__synthesize_comm has a single caller and it > always passes the value 1). Let's fix that. > > Add the full input argument to __event__synthesize_thread which passes > it to perf_event__synthesize_comm. For thread/process monitoring set full > to 0 which means COMM and MMAP events are only generated for the pid > passed to it. For system wide monitoring set full to 1 so that COMM events > are generated for all threads in a process. > > Signed-off-by: David Ahern <dsahern@gmail.com> > --- > tools/perf/util/event.c | 35 ++++++++++++++++++++++++++++++----- > 1 files changed, 30 insertions(+), 5 deletions(-) > > diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c > index 437f8ca..6085727 100644 > --- a/tools/perf/util/event.c > +++ b/tools/perf/util/event.c > @@ -260,10 +260,10 @@ int perf_event__synthesize_modules(perf_event__handler_t process, > > static int __event__synthesize_thread(union perf_event *comm_event, > union perf_event *mmap_event, > - pid_t pid, perf_event__handler_t process, > + pid_t pid, int full, perf_event__handler_t process, > struct perf_session *session) > { > - pid_t tgid = perf_event__synthesize_comm(comm_event, pid, 1, process, > + pid_t tgid = perf_event__synthesize_comm(comm_event, pid, full, process, > session); > if (tgid == -1) > return -1; > @@ -276,7 +276,7 @@ int perf_event__synthesize_thread_map(struct thread_map *threads, > struct perf_session *session) > { > union perf_event *comm_event, *mmap_event; > - int err = -1, thread; > + int err = -1, thread, j; > > comm_event = malloc(sizeof(comm_event->comm) + session->id_hdr_size); > if (comm_event == NULL) > @@ -289,11 +289,36 @@ int perf_event__synthesize_thread_map(struct thread_map *threads, > err = 0; > for (thread = 0; thread < threads->nr; ++thread) { > if (__event__synthesize_thread(comm_event, mmap_event, > - threads->map[thread], > + threads->map[thread], 0, > process, session)) { > err = -1; > break; > } > + > + /* > + * comm.pid is set to thread group id by > + * perf_event__synthesize_comm > + */ > + if ((int) comm_event->comm.pid != threads->map[thread]) { > + bool need_leader = true; > + > + /* is thread group leader in thread_map? */ > + for (j = 0; j < threads->nr; ++j) { > + if ((int) comm_event->comm.pid == threads->map[j]) { > + need_leader = false; > + break; > + } > + } > + > + /* if not, generate events for it */ > + if (need_leader && > + __event__synthesize_thread(comm_event, mmap_event, > + comm_event->comm.pid, 0, > + process, session)) { > + err = -1; > + break; > + } > + } > } > free(mmap_event); > out_free_comm: > @@ -329,7 +354,7 @@ int perf_event__synthesize_threads(perf_event__handler_t process, > if (*end) /* only interested in proper numerical dirents */ > continue; > > - __event__synthesize_thread(comm_event, mmap_event, pid, > + __event__synthesize_thread(comm_event, mmap_event, pid, 1, > process, session); > } >
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