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 <peterz@infradead.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-v3lnpwgrr8mllcr3ntduuqvc@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/python/twatch.py

@@ -19,7 +19,7 @@ def main():
 	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);