linux-kernel - Re: [PATCH v1 08/15] perf record: write trace data into mmap trace files

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Date:   Wed, 14 Oct 2020 15:09:00 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 08/15] perf record: write trace data into mmap trace
 files

Hi,

On 14.10.2020 13:52, Namhyung Kim wrote:
> Hi,
> 
> On Mon, Oct 12, 2020 at 6:01 PM Alexey Budankov
> <alexey.budankov@...ux.intel.com> wrote:
>>
>>
>> Write trace data into per mmap trace files located
>> at data directory. Streaming thread adjusts its affinity
>> according to mask of the buffer being processed.
>>
>> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
>> ---
> [SNIP]
>> @@ -1184,8 +1203,12 @@ static int record__mmap_read_evlist(struct record *rec, struct evlist *evlist,
>>         /*
>>          * Mark the round finished in case we wrote
>>          * at least one event.
>> +        *
>> +        * No need for round events in directory mode,
>> +        * because per-cpu maps and files have data
>> +        * sorted by kernel.
>>          */
>> -       if (bytes_written != rec->bytes_written)
>> +       if (!record__threads_enabled(rec) && bytes_written != rec->bytes_written)
>>                 rc = record__write(rec, NULL, &finished_round_event, sizeof(finished_round_event));
> 
> This means it needs to keep all events in the ordered events queue
> when perf report processes the data, right?

Looks so.

Alexei