linux-kernel - Re: [PATCH] perf annotate: Remove hist__account

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Date:   Thu, 14 Mar 2019 22:17:07 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH] perf annotate: Remove hist__account_cycles from callback



On 3/14/2019 8:04 PM, Jiri Olsa wrote:
> On Wed, Mar 13, 2019 at 04:22:54AM +0800, Jin Yao wrote:
>> The hist__account_cycles is executed when the hist_iter__branch_callback
>> is called. But it looks it's not necessary. In hist__account_cycles, it
>> already walks on all branch entries.
>>
>> This patch moves the hist__account_cycles out of callback, now the data
>> processing is much faster than before.
>>
>> For example,
>> perf record -b ...
>> perf annotate
>>
>> The before/after output should be no change.
> 
> so in the old code it was called multiple times per sample,
> while after your change it's called just once per sample
> 
> it increases cycles stats for symbol, so it's strange
> the behaviour is the same.. could you please exaplin this
> in more detail?
> 

In __symbol__account_cycles,
ch[offset].num_aggr++;
ch[offset].cycles_aggr += cycles;

In annotation__compute_ipc,
al = notes->offsets[offset];
al->cycles = ch->cycles_aggr / ch->num_aggr;

So the num_aggr and cycles_aggr are both increased n times, then the 
final result is the same.

>>
>> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
>> ---
>>   tools/perf/builtin-annotate.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/perf/builtin-annotate.c b/tools/perf/builtin-annotate.c
>> index 67f9d9f..77deb3a 100644
>> --- a/tools/perf/builtin-annotate.c
>> +++ b/tools/perf/builtin-annotate.c
>> @@ -159,8 +159,6 @@ static int hist_iter__branch_callback(struct hist_entry_iter *iter,
>>   	struct perf_evsel *evsel = iter->evsel;
>>   	int err;
>>   
>> -	hist__account_cycles(sample->branch_stack, al, sample, false);
>> -
> 
> there's similar code in perf report, could you please cover
> that as well?
> 

Sure, let me have a try.

Thanks
Jin Yao

> thanks,
> jirka
> 
>>   	bi = he->branch_info;
>>   	err = addr_map_symbol__inc_samples(&bi->from, sample, evsel);
>>   
>> @@ -199,6 +197,8 @@ static int process_branch_callback(struct perf_evsel *evsel,
>>   	if (a.map != NULL)
>>   		a.map->dso->hit = 1;
>>   
>> +	hist__account_cycles(sample->branch_stack, al, sample, false);
>> +
>>   	ret = hist_entry_iter__add(&iter, &a, PERF_MAX_STACK_DEPTH, ann);
>>   	return ret;
>>   }
>> -- 
>> 2.7.4
>>