linux-kernel - Re: [PATCH v2 2/4] perf record: implement -z=<level> and --mmap-flush=<thres> options

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Date:   Wed, 20 Feb 2019 17:13:59 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] perf record: implement -z=<level> and
 --mmap-flush=<thres> options


On 12.02.2019 16:08, Jiri Olsa wrote:
> On Mon, Feb 11, 2019 at 11:22:38PM +0300, Alexey Budankov wrote:
> 
> SNIP
> 
>>  static void record__init_features(struct record *rec)
>> @@ -838,6 +881,9 @@ static void record__init_features(struct record *rec)
>>  	if (!(rec->opts.use_clockid && rec->opts.clockid_res_ns))
>>  		perf_header__clear_feat(&session->header, HEADER_CLOCKID);
>>  
>> +	if (!record__comp_enabled(rec))
>> +		perf_header__clear_feat(&session->header, HEADER_COMPRESSED);
>> +
>>  	perf_header__clear_feat(&session->header, HEADER_STAT);
>>  }
>>  
>> @@ -1147,6 +1193,10 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>>  	fd = perf_data__fd(data);
>>  	rec->session = session;
>>  
>> +	rec->opts.comp_level = 0;
>> +	session->header.env.comp_level = rec->opts.comp_level;
>> +	session->header.env.comp_type = PERF_COMP_NONE;
> 
> hum I think both record and session are zerod from start,
> so this seems superfluous

Removed.

> 
> SNIP
> 
>> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
>> index dec6d218c31c..5ad3a27a042f 100644
>> --- a/tools/perf/util/header.c
>> +++ b/tools/perf/util/header.c
>> @@ -1463,6 +1463,21 @@ static int write_mem_topology(struct feat_fd *ff __maybe_unused,
>>  	return ret;
>>  }
>>  
>> +static int write_compressed(struct feat_fd *ff __maybe_unused,
>> +			    struct perf_evlist *evlist __maybe_unused)
>> +{
>> +	int ret;
>> +	u64 compression_info = ((u64)ff->ph->env.comp_type  << 32) | ff->ph->env.comp_level;
>> +
>> +	ret = do_write(ff, &compression_info, sizeof(compression_info));
>> +	if (ret)
>> +		return ret;
>> +
>> +	compression_info = ((u64)ff->ph->env.comp_ratio << 32) | ff->ph->env.comp_mmap_len;
> 
> let's not complicate this, if you have two u32 values
> to store, store two u32 values ;-)

Corrected.

> 
> also please add version in case we will add new fields in the future,
> so we can stay backward compatible

Implemented.

Thanks,
Alexey

> 
> jirka
>