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SubjectRe: [PATCH 8/9] perf kvm: debug for missing vmexit/vmentry event
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@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 | 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
> vcpu_record.
>
> 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.

David


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