perf python: Use attr.watermark in twatch.py

We want to be woken up for every PERF_RECORD_ event, attr.wakeup_events
is only for PERF_RECORD_SAMPLE, so also use attr.watermark = 1 to fix
that.

Suggested-by: Peter Zijlstra <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Frederic Weisbecker <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/python/twatch.py

···
 	cpus = perf.cpu_map()
 	threads = perf.thread_map()
 	evsel = perf.evsel(task = 1, comm = 1, mmap = 0,
-			   wakeup_events = 1, sample_period = 1,
+			   wakeup_events = 1, watermark = 1,
 			   sample_id_all = 1,
 			   sample_type = perf.SAMPLE_PERIOD | perf.SAMPLE_TID | perf.SAMPLE_CPU | perf.SAMPLE_TID)
 	evsel.open(cpus = cpus, threads = threads);