In this commit:
commit 363b785f38
Author: Don Zickus <dzickus@redhat.com>
Date: Fri Mar 14 10:43:44 2014 -0400
perf tools: Speed up thread map generation
We ended up emitting PERF_RECORD_FORK events after their corresponding
PERF_RECORD_COMM, so the code below will remove the "existing thread"
and then recreates it, unnecessarily:
[root@ssdandy ~]# perf probe -x ~/bin/perf -L machine__process_fork_event
<machine__process_fork_event@/home/acme/git/linux/tools/perf/util/machine.c:0>
0 int machine__process_fork_event(struct machine *machine, union perf_event *event,
struct perf_sample *sample)
2 {
3 struct thread *thread = machine__find_thread(machine,
event->fork.pid,
event->fork.tid);
6 struct thread *parent = machine__findnew_thread(machine,
event->fork.ppid,
event->fork.ptid);
/* if a thread currently exists for the thread id remove it */
if (thread != NULL)
12 machine__remove_thread(machine, thread);
14 thread = machine__findnew_thread(machine, event->fork.pid,
event->fork.tid);
16 if (dump_trace)
17 perf_event__fprintf_task(event, stdout);
19 if (thread == NULL || parent == NULL ||
20 thread__fork(thread, parent, sample->time) < 0) {
21 dump_printf("problem processing PERF_RECORD_FORK, skipping event.\n");
22 return -1;
}
25 return 0;
26 }
[root@ssdandy ~]# perf probe -x ~/bin/perf fork_after_comm=machine__process_fork_event:12
Added new event:
probe_perf:fork_after_comm (on machine__process_fork_event:12 in /home/acme/bin/perf)
You can now use it in all perf tools, such as:
perf record -e probe_perf:fork_after_comm -aR sleep 1
[root@ssdandy ~]#
[root@ssdandy ~]# perf record -g -e probe_perf:* trace -o /tmp/bla
^C[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.021 MB perf.data (30 samples) ]
Terminated
[root@ssdandy ~]#
[root@ssdandy ~]# perf report --no-children --show-total-period --stdio
# To display the perf.data header info, please use --header/--header-only options.
#
# Samples: 30 of event 'probe_perf:fork_after_comm'
# Event count (approx.): 30
#
# Overhead Period Command Shared Object Symbol
# ........ ............ ....... ............. ...............................
#
100.00% 30 trace trace [.] machine__process_fork_event
|
---machine__process_fork_event
__event__synthesize_thread.part.2
perf_event__synthesize_threads
cmd_trace
main
__libc_start_main
[root@ssdandy ~]#
And Looking at 'perf report -D' output we see it:
0 0 0x8698 [0x30]: PERF_RECORD_COMM: auditd:703/707
0 0 0x86c8 [0x38]: PERF_RECORD_FORK(703:707):(703:703)
Fix it by more closely mimicking how the kernel generates those records
when a new fork happens, i.e. first a PERF_RECORD_FORK, then a
PERF_RECORD_COMM.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-h0emvymi2t3mw8dlqd6d6z73@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
4aa5f4f7bb