From defd8d38773cf9e01c69a903d04d5895b78ee74f Mon Sep 17 00:00:00 2001 From: David Ahern Date: Thu, 22 Dec 2011 11:30:01 -0700 Subject: perf tools: Fix comm for processes with named threads 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. The end result (looping over thread_map + synthesizing comm events for each thread each time) 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. Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1324578603-12762-2-git-send-email-dsahern@gmail.com Signed-off-by: David Ahern Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/event.c | 37 ++++++++++++++++++++++++++++++++----- 1 file changed, 32 insertions(+), 5 deletions(-) (limited to 'tools') diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c index b7c7f39a8f6d..a5787260181a 100644 --- a/tools/perf/util/event.c +++ b/tools/perf/util/event.c @@ -261,11 +261,12 @@ int perf_event__synthesize_modules(struct perf_tool *tool, 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_tool *tool, struct machine *machine) { - pid_t tgid = perf_event__synthesize_comm(tool, comm_event, pid, 1, + pid_t tgid = perf_event__synthesize_comm(tool, comm_event, pid, full, process, machine); if (tgid == -1) return -1; @@ -279,7 +280,7 @@ int perf_event__synthesize_thread_map(struct perf_tool *tool, struct machine *machine) { union perf_event *comm_event, *mmap_event; - int err = -1, thread; + int err = -1, thread, j; comm_event = malloc(sizeof(comm_event->comm) + machine->id_hdr_size); if (comm_event == NULL) @@ -292,11 +293,37 @@ int perf_event__synthesize_thread_map(struct perf_tool *tool, 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, tool, machine)) { 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, tool, machine)) { + err = -1; + break; + } + } } free(mmap_event); out_free_comm: @@ -333,7 +360,7 @@ int perf_event__synthesize_threads(struct perf_tool *tool, 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, tool, machine); } -- cgit v1.2.3