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SubjectRe: [PATCH v4 3/4] perf stat: Copy counts from prev_raw_counts to evsel->counts
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Hi Jiri,

On 5/13/2020 11:31 PM, Jiri Olsa wrote:
> On Fri, May 08, 2020 at 03:58:16PM +0800, Jin Yao wrote:
>> It would be useful to support the overall statistics for perf-stat
>> interval mode. For example, report the summary at the end of
>> "perf-stat -I" output.
>>
>> But since perf-stat can support many aggregation modes, such as
>> --per-thread, --per-socket, -M and etc, we need a solution which
>> doesn't bring much complexity.
>>
>> The idea is to use 'evsel->prev_raw_counts' which is updated in
>> each interval and it's saved with the latest counts. Before reporting
>> the summary, we copy the counts from evsel->prev_raw_counts to
>> evsel->counts, and next we just follow non-interval processing.
>>
>> In evsel__compute_deltas, this patch saves counts to the member
>> [cpu0,thread0] of perf_counts for AGGR_GLOBAL.
>>
>> That's because after copying evsel->prev_raw_counts to evsel->counts,
>> perf_counts(evsel->counts, cpu, thread) are all 0 for AGGR_GLOBAL.
>> Once we go to process_counter_maps again, all members of perf_counts
>> are 0.
>>
>> So this patch uses a trick that saves the previous aggr value to
>> the member [cpu0,thread0] of perf_counts, then aggr calculation
>> in process_counter_values can work correctly.
>>
>> v4:
>> ---
>> Change the commit message.
>> No functional change.
>>
>> Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
>> ---
>> tools/perf/util/evsel.c | 1 +
>> tools/perf/util/stat.c | 24 ++++++++++++++++++++++++
>> tools/perf/util/stat.h | 1 +
>> 3 files changed, 26 insertions(+)
>>
>> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
>> index 28683b0eb738..6fae1ec28886 100644
>> --- a/tools/perf/util/evsel.c
>> +++ b/tools/perf/util/evsel.c
>> @@ -1283,6 +1283,7 @@ void evsel__compute_deltas(struct evsel *evsel, int cpu, int thread,
>> if (cpu == -1) {
>> tmp = evsel->prev_raw_counts->aggr;
>> evsel->prev_raw_counts->aggr = *count;
>> + *perf_counts(evsel->prev_raw_counts, 0, 0) = *count;
>
> ok, I think I understand that now.. it's only for AGGR_GLOBAL mode,
> because the perf_stat_process_counter will create aggr values from
> per cpu values
>
> but why do we need to do that all the time? can't we just set it up
> before you zero prev_raw_counts in next patch?
>
>
> if (interval) {
> stat_config.interval = 0;
> stat_config.summary = true;
> perf_evlist__copy_prev_raw_counts(evsel_list);
>
> -> for AGGR_GLOBAL set the counts[0,0] to prev_raw_counts->aggr
>
> perf_evlist__reset_prev_raw_counts(evsel_list);
> runtime_stat_reset(&stat_config);
> perf_stat__reset_shadow_per_stat(&rt_stat);
> }
>


Yes, I think that's a good idea.

Now in v5, I create a new patch "perf stat: Save aggr value to first member of
prev_raw_counts" to save aggr value to first member of prev_raw_counts for
AGGR_GLOBAL. Then next, perf_stat_process_counter can create aggr values from
per cpu values successfully.

Thanks
Jin Yao

>
> thanks,
> jirka
>

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