[PATCH 12/16] perf kvm: option to print events that exceed a threshold

David Ahern
2013-05-26T00:28:04Z

This is useful to spot high latency blips.

Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Runzhen Wang <runzhen@linux.vnet.ibm.com>
---
tools/perf/builtin-kvm.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index 9336737..c2fede6 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -106,6 +106,7 @@ struct perf_kvm_stat {
u64 total_time;
u64 total_count;
u64 lost_events;
+ u64 threshold;

struct rb_root result;

@@ -470,7 +471,7 @@ static bool update_kvm_event(struct kvm_event *event, int vcpu_id,
static bool handle_end_event(struct perf_kvm_stat *kvm,
struct vcpu_event_record *vcpu_record,
struct event_key *key,
- u64 timestamp)
+ struct perf_sample *sample)
{
struct kvm_event *event;
u64 time_begin, time_diff;
@@ -507,12 +508,24 @@ static bool handle_end_event(struct perf_kvm_stat *kvm,
vcpu_record->start_time = 0;

/* seems to happen once in a while during live mode */
- if (timestamp < time_begin) {
+ if (sample->time < time_begin) {
pr_debug("End time before begin time; skipping event.\n");
return true;
}

- time_diff = timestamp - time_begin;
+ time_diff = sample->time - time_begin;
+
+ if (kvm->threshold && time_diff > kvm->threshold) {
+ char decode[32];
+
+ kvm->events_ops->decode_key(kvm, &event->key, decode);
+ if (strcmp(decode, "HLT")) {
+ pr_info("%" PRIu64 " VM %d, vcpu %d: %s event took %" PRIu64 "usec\n",
+ sample->time, sample->pid, vcpu_record->vcpu_id,
+ decode, time_diff/1000);
+ }
+ }
+
return update_kvm_event(event, vcpu, time_diff);
}

@@ -559,7 +572,7 @@ static bool handle_kvm_event(struct perf_kvm_stat *kvm,
return handle_begin_event(kvm, vcpu_record, &key, sample->time);

if (kvm->events_ops->is_end_event(evsel, sample, &key))
- return handle_end_event(kvm, vcpu_record, &key, sample->time);
+ return handle_end_event(kvm, vcpu_record, &key, sample);

return true;
}
@@ -1333,6 +1346,8 @@ static int kvm_events_live(struct perf_kvm_stat *kvm,
OPT_STRING('k', "key", &kvm->sort_key, "sort-key",
"key for sorting: sample(sort by samples number)"
" time (sort by avg time)"),
+ OPT_U64('T', "threshold", &kvm->threshold,
+ "show events that take longer than threshold usecs"),
OPT_END()
};
const char * const live_usage[] = {
@@ -1363,6 +1378,7 @@ static int kvm_events_live(struct perf_kvm_stat *kvm,

use_browser = 0;
setup_browser(false);
+ kvm->threshold *= 1000; /* convert usec to nsec */

if (argc) {
argc = parse_options(argc, argv, live_options,
--
1.7.10.1