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Date: Tue, 7 Jul 2020 17:55:14 +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 07.07.2020 17:23, Jiri Olsa wrote:
> On Tue, Jul 07, 2020 at 04:24:28PM +0300, Alexey Budankov wrote:
>>
>> On 07.07.2020 16:14, Jiri Olsa wrote:
>>> On Tue, Jul 07, 2020 at 04:07:42PM +0300, Alexey Budankov wrote:
>>>>
>>>> On 06.07.2020 22:34, Jiri Olsa wrote:
>>>>> On Mon, Jul 06, 2020 at 05:47:54PM +0300, Alexey Budankov wrote:
>>>>>>
>>>>>> 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 <===
>>>>>
>>>>> ok, but we could still take handle_interval out of process_evlist
>>>>> and the interval process will be more clear for me (with some
>>>>> additional comments in the code) ... perhaps something like below?
>>>>>
>>>>> thanks,
>>>>> jirka
>>>>>
>>>>>
>>>>> ---
>>>>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>>>>> index 5021f7286422..af83bf6b2db0 100644
>>>>> --- a/tools/perf/builtin-stat.c
>>>>> +++ b/tools/perf/builtin-stat.c
>>>>> @@ -485,19 +485,18 @@ static bool handle_interval(unsigned int interval, int *times)
>>>>> return false;
>>>>> }
>>>>>
>>>>> -static bool process_evlist(struct evlist *evlist, unsigned int interval, int *times)
>>>>> +static bool process_evlist(struct evlist *evlist)
>>>>> {
>>>>> - bool stop = false;
>>>>> enum evlist_ctl_cmd cmd = EVLIST_CTL_CMD_UNSUPPORTED;
>>>>> + bool enabled = false;
>>>>>
>>>>> if (evlist__ctlfd_process(evlist, &cmd) > 0) {
>>>>> switch (cmd) {
>>>>> case EVLIST_CTL_CMD_ENABLE:
>>>>> pr_info(EVLIST_ENABLED_MSG);
>>>>> - stop = handle_interval(interval, times);
>>>>> + enabled = true;
>>>>> break;
>>>>> case EVLIST_CTL_CMD_DISABLE:
>>>>> - stop = handle_interval(interval, times);
>>>>> pr_info(EVLIST_DISABLED_MSG);
>>>>> break;
>>>>> case EVLIST_CTL_CMD_ACK:
>>>>> @@ -507,7 +506,7 @@ static bool process_evlist(struct evlist *evlist, unsigned int interval, int *ti
>>>>> }
>>>>> }
>>>>>
>>>>> - return stop;
>>>>> + return enabled;
>>>>> }
>>>>>
>>>>> static void enable_counters(void)
>>>>> @@ -618,7 +617,8 @@ static int dispatch_events(bool forks, int timeout, int interval, int *times)
>>>>> stop = handle_interval(interval, times);
>>>>> time_to_sleep = sleep_time;
>>>>> } else { /* fd revent */
>>>>> - stop = process_evlist(evsel_list, interval, times);
>>>>> + if (process_evlist(evsel_list))
>>>>> + stop = handle_interval(interval, times);
>>>>
>>>> It will call only on enable command and lead to artificial spikes in the beginning of interval.
>>>> May be just take handle_interval() out of process_evlist() and have it similar to record case?
>>>
>>> it can be called also for disable case then
>>
>>
>> Made it like this so now times counter is not affected during commands processing:
>
> hm, can't process list just return true
> when the interval needs to be printed?
process_evlist() now looks suboptimal since record mode code directly calls evlist__ctlfd_process()
and then handles returned command specifically to the mode. So in v10 I replaced process_evlist()
call with direct evlist__ctlfd_process() call and then handling the returned command by printing
command msg tag and counter values in the required order. Like this:
+ clock_gettime(CLOCK_MONOTONIC, &time_start);
+ if (!(evlist__poll(evsel_list, time_to_sleep) > 0)) { /* poll timeout or EINTR */
+ if (timeout)
+ break;
+ else
+ stop = handle_interval(interval, times);
+ time_to_sleep = sleep_time;
+ } else { /* fd revent */
+ if (evlist__ctlfd_process(evsel_list, &cmd) > 0) {
+ if (interval) {
+ switch (cmd) {
+ case EVLIST_CTL_CMD_ENABLE:
+ pr_info(EVLIST_ENABLED_MSG);
+ process_interval();
+ break;
+ case EVLIST_CTL_CMD_DISABLE:
+ process_interval();
+ pr_info(EVLIST_DISABLED_MSG);
+ break;
+ case EVLIST_CTL_CMD_ACK:
+ case EVLIST_CTL_CMD_UNSUPPORTED:
+ default:
+ break;
+ }
+ }
+ }
+ clock_gettime(CLOCK_MONOTONIC, &time_stop);
+ compute_tts(&time_start, &time_stop, &time_to_sleep);
+ }
Alexey
>
> jirka
>
>>
>> static void process_evlist(struct evlist *evlist, enum evlist_ctl_cmd *cmd)
>> {
>> if (evlist__ctlfd_process(evlist, cmd) > 0) {
>> switch (*cmd) {
>> case EVLIST_CTL_CMD_ENABLE:
>> pr_info(EVLIST_ENABLED_MSG);
>> break;
>> case EVLIST_CTL_CMD_DISABLE:
>> pr_info(EVLIST_DISABLED_MSG);
>> break;
>> case EVLIST_CTL_CMD_ACK:
>> case EVLIST_CTL_CMD_UNSUPPORTED:
>> default:
>> break;
>> }
>> }
>> }
>>
>> ...
>>
>> clock_gettime(CLOCK_MONOTONIC, &time_start);
>> if (!(evlist__poll(evsel_list, time_to_sleep) > 0)) { /* poll timeout or EINTR */
>> if (timeout)
>> break;
>> else
>> stop = handle_interval(interval, times);
>> time_to_sleep = sleep_time;
>> } else { /* fd revent */
>> process_evlist(evsel_list, &cmd);
>> if (interval) {
>> switch (cmd) {
>> case EVLIST_CTL_CMD_ENABLE:
>> case EVLIST_CTL_CMD_DISABLE:
>> process_interval();
>> case EVLIST_CTL_CMD_ACK:
>> case EVLIST_CTL_CMD_UNSUPPORTED:
>> default:
>> break;
>> }
>> }
>> clock_gettime(CLOCK_MONOTONIC, &time_stop);
>> compute_tts(&time_start, &time_stop, &time_to_sleep);
>> }
>>
>> Alexey
>>
>
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