linux-kernel - Re: [PATCH v8 20/22] perf session: Load data directory files for analysis

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Date:   Fri, 2 Jul 2021 15:04:24 +0300
From:   "Bayduraev, Alexey V" <alexey.v.bayduraev@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Antonov <alexander.antonov@...ux.intel.com>,
        Alexei Budankov <abudankov@...wei.com>,
        Riccardo Mancini <rickyman7@...il.com>
Subject: Re: [PATCH v8 20/22] perf session: Load data directory files for
 analysis


On 02.07.2021 13:30, Jiri Olsa wrote:
> On Wed, Jun 30, 2021 at 06:54:59PM +0300, Alexey Bayduraev wrote:
> 
> SNIP
> 
>> +	while ((ret >= 0) && readers) {
>> +		if (session_done())
>> +			return 0;
>> +
>> +		if (rd[i].state.eof) {
>> +			i = (i + 1) % session->nr_readers;
>> +			continue;
>> +		}
>> +
>> +		ret = reader__read_event(&rd[i], session, &prog);
>> +		if (ret < 0)
>> +			break;
>> +		if (ret == READER_EOF) {
>> +			ret = reader__mmap(&rd[i], session);
>> +			if (ret < 0)
>> +				goto out_err;
>> +			if (ret == READER_EOF)
>> +				readers--;
>> +		}
>> +
>> +		/*
>> +		 * Processing 10MBs of data from each reader in sequence,
>> +		 * because that's the way the ordered events sorting works
>> +		 * most efficiently.
>> +		 */
>> +		if (rd[i].state.size >= 10*1024*1024) {
>> +			rd[i].state.size = 0;
>> +			i = (i + 1) % session->nr_readers;
>> +		}
> 
> hi,
> so this was sort of hack to make this faster.. we need some
> justification for this and make that configurable as well,
> if we keep it

Hi,

I am currently thinking of another round-robin read algorithm, based on
timestamps with periodical ordered_queue flushing after each round, this
might be better, but I'm not sure if this should be included in this patchset. 

Probably introduction of new constant will be enough for current implementation.

Regards,
Alexey

> 
> jirka
>