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Date: Mon, 6 Jul 2020 17:47:54 +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>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Andi Kleen <ak@...ux.intel.com>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 11/15] perf stat: implement control commands handling
On 06.07.2020 15:34, Jiri Olsa wrote:
> On Fri, Jul 03, 2020 at 10:47:22AM +0300, Alexey Budankov wrote:
>>
>> Implement handling of 'enable' and 'disable' control commands
>> coming from control file descriptor. process_evlist() function
>> checks for events on control fds and makes required operations.
>> If poll event splits initiated timeout interval then the reminder
>> is calculated and still waited in the following poll() syscall.
>>
>> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
>> ---
>> tools/perf/builtin-stat.c | 75 ++++++++++++++++++++++++++++-----------
>> 1 file changed, 55 insertions(+), 20 deletions(-)
>>
>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>> index 9e4288ecf2b8..5021f7286422 100644
>> --- a/tools/perf/builtin-stat.c
>> +++ b/tools/perf/builtin-stat.c
>> @@ -485,6 +485,31 @@ static bool handle_interval(unsigned int interval, int *times)
>> return false;
>> }
>>
>> +static bool process_evlist(struct evlist *evlist, unsigned int interval, int *times)
>> +{
>> + bool stop = false;
>> + enum evlist_ctl_cmd cmd = EVLIST_CTL_CMD_UNSUPPORTED;
>> +
>> + if (evlist__ctlfd_process(evlist, &cmd) > 0) {
>> + switch (cmd) {
>> + case EVLIST_CTL_CMD_ENABLE:
>> + pr_info(EVLIST_ENABLED_MSG);
>> + stop = handle_interval(interval, times);
>> + break;
>> + case EVLIST_CTL_CMD_DISABLE:
>> + stop = handle_interval(interval, times);
>
> I still don't understand why you call handle_interval in here
>
> I don't see it being necessary.. you enable events and handle_interval,
> wil be called in the next iteration of dispatch_events, why complicate
> this function with that?
Printing event counts at the moment of command processing lets scripts
built on top of stat output to provide more plain and accurate metrics.
Otherwise it may get spikes in the beginning of the next time interval
because not all counts lay inside [Events enabled, Events disable]
If -I interval is large tail event count can be also large. Compare the
output below with the output in the cover letter. Either way is possible
but the latter one likely complicates the scripts I mentioned above.
perf=tools/perf/perf
${perf} stat -D -1 -e cpu-cycles -a -I 1000 \
--control fd:${ctl_fd},${ctl_fd_ack} \
-- sleep 40 &
Events disabled
# time counts unit events
1.001100723 <not counted> cpu-cycles
2.003146566 <not counted> cpu-cycles
3.005073317 <not counted> cpu-cycles
4.006337062 <not counted> cpu-cycles
Events enabled
enable acked(ack)
5.011182000 54,128,692 cpu-cycles <===
6.012300167 3,648,804,827 cpu-cycles
7.013631689 590,438,536 cpu-cycles
8.015558583 406,935,663 cpu-cycles
9.017455505 407,806,862 cpu-cycles
10.019300780 399,351,824 cpu-cycles
11.021180025 404,584,417 cpu-cycles
12.023033661 537,787,981 cpu-cycles
13.024422354 699,395,364 cpu-cycles
14.026325749 397,871,324 cpu-cycles
disable acked()
Events disabled
15.027857981 396,956,159 cpu-cycles <===
16.029279264 <not counted> cpu-cycles
17.031131311 <not counted> cpu-cycles
18.033010580 <not counted> cpu-cycles
19.034918883 <not counted> cpu-cycles
enable acked(ack)
Events enabled
20.036758793 183,544,975 cpu-cycles <===
21.038163289 419,054,544 cpu-cycles
22.040108245 413,993,309 cpu-cycles
23.042042365 403,584,493 cpu-cycles
24.043985381 416,512,094 cpu-cycles
25.045925682 401,513,429 cpu-cycles
# time counts unit events
26.047822238 461,205,096 cpu-cycles
27.049784263 414,319,162 cpu-cycles
28.051745360 403,706,915 cpu-cycles
29.053674600 416,502,883 cpu-cycles
disable acked()
Events disabled
30.054750685 414,184,409 cpu-cycles <===
Alexey
>
> thanks,
> jirka
>
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