Re: [PATCH v8 12/13] perf record: implement control commands handling

Alexey Budankov
2020-06-24T14:55:07Z

On 24.06.2020 17:00, Alexey Budankov wrote:
>
> On 23.06.2020 17:54, Jiri Olsa wrote:
>> On Wed, Jun 17, 2020 at 11:43:58AM +0300, Alexey Budankov wrote:
>>>
>>> Implement handling of 'enable' and 'disable' control commands
>>> coming from control file descriptor.
>>>
>>> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
>>> ---
>>> tools/perf/builtin-record.c | 16 ++++++++++++++++
>>> 1 file changed, 16 insertions(+)
>>>
>>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>>> index d0b29a1070a0..0394e068dde8 100644
>>> --- a/tools/perf/builtin-record.c
>>> +++ b/tools/perf/builtin-record.c
>>> @@ -1527,6 +1527,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>>> bool disabled = false, draining = false;
>>> int fd;
>>> float ratio = 0;
>>> + enum evlist_ctl_cmd cmd = EVLIST_CTL_CMD_UNSUPPORTED;
>>>
>>> atexit(record__sig_exit);
>>> signal(SIGCHLD, sig_handler);
>>> @@ -1830,6 +1831,21 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>>> alarm(rec->switch_output.time);
>>> }
>>>
>>> + if (evlist__ctlfd_process(rec->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;
>>> + }
>>> + }
>>
>> so there's still the filter call like:
>>
>> if (evlist__filter_pollfd(rec->evlist, POLLERR | POLLHUP) == 0)
>> draining = true;
>>
>> it will never be 0 if the control fds are stil alive no?
>
> Due to change in filter_pollfd() and preceding evlist__ctlfd_process() call
> now control fd is not counted by filter_pollfd().
And evlist__ctlfd_process() still should be called second time right
after evlist_poll() but prior filter_polfd().

~Alexey

>
> However event fds with .revents == 0 are not counted either and this breaks
> the algorithm thus something more is still required to cover this gap.
>
> ~Alexey
>
>>
>> jirka
>>