From: "Jin, Yao" <yao.jin@linux.intel.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: acme@kernel.org, jolsa@kernel.org, peterz@infradead.org,
mingo@redhat.com, alexander.shishkin@linux.intel.com,
Linux-kernel@vger.kernel.org, ak@linux.intel.com,
kan.liang@intel.com, yao.jin@intel.com
Subject: Re: [PATCH v3 3/4] perf stat: Copy counts from prev_raw_counts to evsel->counts
Date: Fri, 8 May 2020 11:34:16 +0800 [thread overview]
Message-ID: <d783c490-e474-ffc7-b388-b6e7734196a6@linux.intel.com> (raw)
In-Reply-To: <20200507151950.GG2804092@krava>
Hi Jiri,
On 5/7/2020 11:19 PM, Jiri Olsa wrote:
> On Thu, May 07, 2020 at 02:58:21PM +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.
>
> I did not realize we already store the count in prev_raw_counts ;-) nice catch!
>
Thanks! :)
>>
>> In evsel__compute_deltas, this patch saves counts to the position
>> of [cpu0,thread0] for AGGR_GLOBAL. After copying counts from
>> evsel->prev_raw_counts to evsel->counts, we don't need to
>> modify process_counter_maps in perf_stat_process_counter to let it
>> work well.
>
> I don't understand why you need to store it in here.. what's the catch
> in process_counter_maps?
>
Sorry, I didn't explain clearly.
You know the idea is to copy evsel->prev_raw_counts to evsel->counts before
reporting the summary.
But for AGGR_GLOBAL (cpu = -1 in perf_evsel__compute_deltas), the
evsel->prev_raw_counts is only stored with the aggr value.
if (cpu == -1) {
tmp = evsel->prev_raw_counts->aggr;
evsel->prev_raw_counts->aggr = *count;
} else {
tmp = *perf_counts(evsel->prev_raw_counts, cpu, thread);
*perf_counts(evsel->prev_raw_counts, cpu, thread) = *count;
}
So after copying evsel->prev_raw_counts to evsel->counts,
perf_counts(evsel->counts, cpu, thread) are all 0.
Once we go to process_counter_maps again, in process_counter_values, count->val
is 0.
case AGGR_GLOBAL:
aggr->val += count->val;
aggr->ena += count->ena;
aggr->run += count->run;
And the aggr->val is 0.
So this patch uses a trick that saves the previous aggr value to cpu0/thread0,
then above aggr->val calculation can work correctly.
Thanks
Jin Yao
> thanks,
> jirka
>
next prev parent reply other threads:[~2020-05-08 3:34 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-07 6:58 [PATCH v3 0/4] perf stat: Support overall statistics for interval mode Jin Yao
2020-05-07 6:58 ` [PATCH v3 1/4] perf stat: Fix wrong per-thread runtime stat " Jin Yao
2020-05-07 15:19 ` Jiri Olsa
2020-05-08 2:03 ` Jin, Yao
2020-05-07 6:58 ` [PATCH v3 2/4] perf counts: Reset prev_raw_counts counts Jin Yao
2020-05-07 15:19 ` Jiri Olsa
2020-05-08 2:45 ` Jin, Yao
2020-05-07 6:58 ` [PATCH v3 3/4] perf stat: Copy counts from prev_raw_counts to evsel->counts Jin Yao
2020-05-07 15:19 ` Jiri Olsa
2020-05-08 3:34 ` Jin, Yao [this message]
2020-05-07 6:58 ` [PATCH v3 4/4] perf stat: Report summary for interval mode Jin Yao
2020-05-07 15:18 ` Jiri Olsa
2020-05-08 1:11 ` Jin, Yao
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