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

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Message-ID: <dcda8374-9bf4-8989-40b5-75b080b26a12@linux.intel.com>
Date:   Wed, 20 Feb 2019 17:14:39 +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 16:09, Jiri Olsa wrote:
> On Mon, Feb 11, 2019 at 11:22:38PM +0300, Alexey Budankov wrote:
> 
> SNIP
> 
>> @@ -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;
>> +
>>  	record__init_features(rec);
>>  
>>  	if (rec->opts.use_clockid && rec->opts.clockid_res_ns)
>> @@ -1176,6 +1226,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>>  		err = -1;
>>  		goto out_child;
>>  	}
>> +	session->header.env.comp_mmap_len = session->evlist->mmap_len;
> 
> so the comp_mmap_len is the max length of the compressed packet?

comp_mmap_len is the size of buffer to encompass one compressed chunk 
of data after its decompression.

> 
> any idea if this value might have some impact on the processing speed?

It increases memory consumption at the loading and processing stages.

> 
> I see you mentioned the size reduction, could you also meassure
> the record overhead?

Let's get back to this after the code review.

Thanks,
Alexey

> 
> thanks,
> jirka
>