linux-kernel - Re: [PATCH v2] perf sched replay: Fix -r/--repeat command line option for infinity

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Date: Fri, 28 Jun 2024 12:39:54 +0530
From: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>, acme@...hat.com,
        Chen Yu <yu.c.chen@...el.com>, Fernand Sieber <sieberf@...zon.com>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, James Clark <james.clark@....com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Ian Rogers
 <irogers@...gle.com>,
        Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
Subject: Re: [PATCH v2] perf sched replay: Fix -r/--repeat command line option
 for infinity

Hi Namhyung,

On 28/06/24 08:41, Namhyung Kim wrote:
> On Fri, Jun 28, 2024 at 08:00:14AM +0530, Madadi Vineeth Reddy wrote:
>> On 21/06/24 22:49, Madadi Vineeth Reddy wrote:
>>> Currently, the -r/--repeat option accepts values from 0 and complains
>>> for -1. The help section specifies:
>>> -r, --repeat <n>      repeat the workload replay N times (-1: infinite)
>>>
>>> The -r -1 option raises an error because replay_repeat is defined as
>>> an unsigned int.
>>>
>>> In the current implementation, the workload is repeated n times when
>>> -r <n> is used, except when n is 0.
>>>
>>> When -r is set to 0, the workload is also repeated once. This happens
>>> because when -r=0, the run_one_test function is not called. (Note that
>>> mutex unlocking, which is essential for child threads spawned to emulate
>>> the workload, happens in run_one_test.) However, mutex unlocking is
>>> still performed in the destroy_tasks function. Thus, -r=0 results in the
>>> workload running once coincidentally.
>>>
>>> To clarify and maintain the existing logic for -r >= 1 (which runs the
>>> workload the specified number of times) and to fix the issue with infinite
>>> runs, make -r=0 perform an infinite run.
>>>
>>> Signed-off-by: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
>>> Reviewed-by: James Clark <james.clark@....com>
>>>
>>
>> Hi all,
>> Any suggestions/comments on this patch?
> 
> I think the original intention was to set replay_repeat to UINT_MAX
> using -1.  But it seems to refuse the negative number now.
> 
> Maybe you can simply set it to UNIT_MAX for -r 0.

Thanks for the feedback. I will make the change and send a v3.

Thanks and Regards
Madadi Vineeth Reddy

> 
> Thanks,
> Namhyung
> 
> 
>>> ---
>>> Changes in v2:
>>> - Kept the existing 'for' loop and added a condition for infinite
>>>   looping. (James Clark)
>>> - This change also ensures that integer overflow doesn't occur when
>>>   'replay_repeat' is zero.
>>> - Add Reviewed-by tag from James Clark.
>>> - Rebase against perf-tools-next commit 788c5160526a ("perf vendor
>>>   events: Add westmereex counter information")
>>> - Link to v1: https://lore.kernel.org/all/20240618112907.15131-1-vineethr@linux.ibm.com/
>>>
>>>  tools/perf/Documentation/perf-sched.txt |  7 +++++++
>>>  tools/perf/builtin-sched.c              | 11 ++++++++---
>>>  2 files changed, 15 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/tools/perf/Documentation/perf-sched.txt b/tools/perf/Documentation/perf-sched.txt
>>> index a216d2991b19..f1be8f0b249e 100644
>>> --- a/tools/perf/Documentation/perf-sched.txt
>>> +++ b/tools/perf/Documentation/perf-sched.txt
>>> @@ -202,6 +202,13 @@ OPTIONS for 'perf sched timehist'
>>>  --state::
>>>  	Show task state when it switched out.
>>>  
>>> +OPTIONS for 'perf sched replay'
>>> +------------------------------
>>> +
>>> +-r::
>>> +--repeat <n>::
>>> +	repeat the workload n times (0: infinite). Default is 10.
>>> +
>>>  SEE ALSO
>>>  --------
>>>  linkperf:perf-record[1]
>>> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
>>> index 8cdf18139a7e..51b3dea404bc 100644
>>> --- a/tools/perf/builtin-sched.c
>>> +++ b/tools/perf/builtin-sched.c
>>> @@ -3383,8 +3383,13 @@ static int perf_sched__replay(struct perf_sched *sched)
>>>  	sched->thread_funcs_exit = false;
>>>  	create_tasks(sched);
>>>  	printf("------------------------------------------------------------\n");
>>> -	for (i = 0; i < sched->replay_repeat; i++)
>>> -		run_one_test(sched);
>>> +	if (sched->replay_repeat == 0) {
>>> +		while (1)
>>> +			run_one_test(sched);
>>> +	} else {
>>> +		for (i = 0; i < sched->replay_repeat; i++)
>>> +			run_one_test(sched);
>>> +	}
>>>  
>>>  	sched->thread_funcs_exit = true;
>>>  	destroy_tasks(sched);
>>> @@ -3548,7 +3553,7 @@ int cmd_sched(int argc, const char **argv)
>>>  	};
>>>  	const struct option replay_options[] = {
>>>  	OPT_UINTEGER('r', "repeat", &sched.replay_repeat,
>>> -		     "repeat the workload replay N times (-1: infinite)"),
>>> +		     "repeat the workload replay N times (0: infinite)"),
>>>  	OPT_PARENT(sched_options)
>>>  	};
>>>  	const struct option map_options[] = {
>>