linux-kernel - Re: [PATCH v2 00/15] Introduce threaded trace streaming for basic perf record operation

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Message-ID: <9c76b415-2610-14f8-37d4-461d0d5c078b@linux.intel.com>
Date:   Tue, 27 Oct 2020 19:01:34 +0300
From:   Alexey Budankov <alexey.budankov@...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>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 00/15] Introduce threaded trace streaming for basic
 perf record operation


On 27.10.2020 15:10, Jiri Olsa wrote:
> On Mon, Oct 26, 2020 at 08:59:01PM +0300, Alexey Budankov wrote:
>>
>> On 24.10.2020 18:43, Jiri Olsa wrote:
>>> On Wed, Oct 21, 2020 at 06:52:43PM +0300, Alexey Budankov wrote:
>>>>
>>>> Changes in v2:
>>>> - explicitly added credit tags to patches 6/15 and 15/15,
>>>>   additionally to cites [1], [2]
>>>> - updated description of 3/15 to explicitly mention the reason
>>>>   to open data directories in read access mode (e.g. for perf report)
>>>> - implemented fix for compilation error of 2/15
>>>> - explicitly elaborated on found issues to be resolved for
>>>>   threaded AUX trace capture
>>>>
>>>> v1: https://lore.kernel.org/lkml/810f3a69-0004-9dff-a911-b7ff97220ae0@linux.intel.com/
>>>>
>>>> Patch set provides threaded trace streaming for base perf record
>>>> operation. Provided streaming mode (--threads) mitigates profiling
>>>> data losses and resolves scalability issues of serial and asynchronous
>>>> (--aio) trace streaming modes on multicore server systems. The patch
>>>> set is based on the prototype [1], [2] and the most closely relates
>>>> to mode 3) "mode that creates thread for every monitored memory map".
>>>
>>> so what I liked about the previous code was that you could
>>> configure how the threads would be created
>>>
>>> default --threads options created thread for each cpu like
>>> in your change:
>>>
>>>   $ perf record -v --threads ...
>>>   ...
>>>   thread 0 monitor: 0 allowed: 0
>>>   thread 1 monitor: 1 allowed: 1
>>>   thread 2 monitor: 2 allowed: 2
>>>   thread 3 monitor: 3 allowed: 3
>>>   thread 4 monitor: 4 allowed: 4
>>>   thread 5 monitor: 5 allowed: 5
>>>   thread 6 monitor: 6 allowed: 6
>>>   thread 7 monitor: 7 allowed: 7
>>
>> Yes, it is configurable in the prototype. Even though this patch set
>> doesn't implement that parameters for --thread option, just because
>> VTune doesn't have use cases for that yet, it has still been designed
>> and implemented with that possible extension in mind so it could then
>> be easily added on top of it.
> 
> I'm not sure about vtune extensions, but if we are going to
> have --threads option I believe we should make it configurable
> at least to the extend descibed below

It employs --threads mode only and there are no use cases
observed so far beyond this mode. Do you have or see such
use cases?

Alexei

> 
> jirka
> 
>>
>>>
>>>
>>> then numa based:
>>>
>>>   $ perf record -v --threads=numa ...
>>>   ...
>>>   thread 0 monitor: 0-5,12-17 allowed: 0-5,12-17
>>>   thread 1 monitor: 6-11,18-23 allowed: 6-11,18-23
>>>
>>>
>>> socket based:
>>>
>>>   $ perf record -v --threads=socket ...
>>>   ...
>>>   thread 0 monitor: 0-7 allowed: 0-7
>>>
>>>
>>> core based:
>>>
>>>   $ perf record -v --threads=core ...
>>>   ...
>>>   thread 0 monitor: 0,4 allowed: 0,4
>>>   thread 1 monitor: 1,5 allowed: 1,5
>>>   thread 2 monitor: 2,6 allowed: 2,6
>>>   thread 3 monitor: 3,7 allowed: 3,7
>>>
>>>
>>> and user configurable:
>>>
>>>   $ perf record -v  --threads=0-3/0:4-7/4 ...
>>>   ...
>>>   threads: 0. monitor 0-3, allowed 0
>>>   threads: 1. monitor 4-7, allowed 4
>>>
>>>
>>> so this way you could easily pin threads to cpu/core/socket/numa,
>>> or to some other cpu of your choice, because this will be always
>>> game of try and check where I'm not getting LOST events and not
>>> creating 1000 threads
>>>
>>>  perf record: Add support for threads numa option value
>>>  perf record: Add support for threads socket option value
>>>  perf record: Add support for threads core option value
>>>  perf record: Add support for threads user option value
>>
>> Makes sense.
>>
>> Alexei
>>
>