Re: [PATCH 8/9] perf kvm: debug for missing vmexit/vmentry event

From: David Ahern
Date: Mon Aug 05 2013 - 11:00:51 EST

On 8/5/13 2:53 AM, Xiao Guangrong wrote:
On 08/03/2013 04:05 AM, David Ahern wrote:
Expected to have missing events for each vcpu when perf is
started. After that should not have missing events.

Sorry, i can not understand what's this info used for.

For debugging. Things that should not happen do seem to happen -- rarely, but it does

Signed-off-by: David Ahern <dsahern@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
Cc: Runzhen Wang <runzhen@xxxxxxxxxxxxxxxxxx>
tools/perf/builtin-kvm.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index 28afc05d..41dd25a 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -568,11 +568,22 @@ static bool handle_kvm_event(struct perf_kvm_stat *kvm,
(kvm->trace_vcpu != vcpu_record->vcpu_id))
return true;

- if (kvm->events_ops->is_begin_event(evsel, sample, &key))
+ if (kvm->events_ops->is_begin_event(evsel, sample, &key)) {
+ if (vcpu_record->start_time) {
+ pr_debug("consecutive begin events (%s) for pid %d, vcpu %d\n",
+ evsel->name, sample->pid, vcpu_record->vcpu_id);
+ }

This is not true, the ->start_time is set in handle_begin_event() for the new alloced

If you just want to know the point where is the first event lost, you can track
it in:

static bool handle_end_event(struct perf_kvm_stat *kvm,
struct vcpu_event_record *vcpu_record,
struct event_key *key,
u64 timestamp)

/* The begin event is not caught. */
if (!time_begin) <======
return true;

Ok. I'll drop the patch. I added it for a reason, but can't remember why at the moment.

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