perf python: Support the PERF_RECORD_SWITCH event

Commit-ID:  ae938802443732e77d01f8d5b52b900b9327ff30
Gitweb:     http://git.kernel.org/tip/ae938802443732e77d01f8d5b52b900b9327ff30
Author:     Arnaldo Carvalho de Melo <[email protected]>
AuthorDate: Tue, 6 Oct 2015 17:46:46 -0300
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Wed, 7 Oct 2015 19:41:50 -0300

perf python: Support the PERF_RECORD_SWITCH event

To test it check tools/perf/python/twatch.py, after following the instructions there to enable context_switch, output looks like:

[root@zoo linux]# tools/perf/python/twatch.py
cpu: 1, pid: 31463, tid: 31463 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31463, switch_out: 0 }
cpu: 2, pid: 31463, tid: 31496 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31496, switch_out: 0 }
cpu: 2, pid: 31463, tid: 31496 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31496, switch_out: 1 }
cpu: 3, pid: 31463, tid: 31527 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31527, switch_out: 0 }
cpu: 1, pid: 31463, tid: 31463 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31463, switch_out: 1 }
cpu: 3, pid: 31463, tid: 31527 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31527, switch_out: 1 }
cpu: 1, pid: 31463, tid: 31463 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31463, switch_out: 0 } ^CTraceback (most recent call last):
File "tools/perf/python/twatch.py", line 67, in <module>
main(context_switch = 1, thread = 31463)
File "tools/perf/python/twatch.py", line 40, in main
evlist.poll(timeout = -1)
KeyboardInterrupt
[root@zoo linux]#

---
 tools/perf/python/twatch.py | 23 +++++++++++++++---
 tools/perf/util/python.c    | 59 ++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 75 insertions(+), 7 deletions(-)

index b9d5083..c235c22 100755
@@ -15,14 +15,14 @@
 
 import perf
 
-def main():
+def main(context_switch = 0, thread = -1):
 	cpus = perf.cpu_map()
-	threads = perf.thread_map()
+	threads = perf.thread_map(thread)
 	evsel = perf.evsel(type	  = perf.TYPE_SOFTWARE,
 			   config = perf.COUNT_SW_DUMMY,
 			   task = 1, comm = 1, mmap = 0, freq = 0,
 			   wakeup_events = 1, watermark = 1,
-			   sample_id_all = 1,
+			   sample_id_all = 1, context_switch = context_switch,
 			   sample_type = perf.SAMPLE_PERIOD | perf.SAMPLE_TID | perf.SAMPLE_CPU)
 
 	"""What we want are just the PERF_RECORD_ lifetime events for threads,

@@ -48,4 +48,21 @@ def main():
 			print event
 
 if __name__ == '__main__':
+    """
+	To test the PERF_RECORD_SWITCH record, pick a pid and replace
+	in the following line.
+
+	Example output:
+
+cpu: 3, pid: 31463, tid: 31593 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31593, switch_out: 1 }
+cpu: 1, pid: 31463, tid: 31489 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31489, switch_out: 1 }
+cpu: 2, pid: 31463, tid: 31496 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31496, switch_out: 1 }
+cpu: 3, pid: 31463, tid: 31491 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31491, switch_out: 0 }
+
+	It is possible as well to use event.misc & perf.PERF_RECORD_MISC_SWITCH_OUT
+	to figure out if this is a context switch in or out of the monitored threads.
+
+	If bored, please add command line option parsing support for these options :-)
+    """
+    # main(context_switch = 1, thread = 31463)
     main()