On 09.04.2018 12:26, Peter Zijlstra wrote:
> On Mon, Apr 09, 2018 at 10:25:32AM +0300, Alexey Budankov wrote:
>>
>> Store preempting context switch out event into Perf trace as a part of
>> PERF_RECORD_SWITCH[_CPU_WIDE] record.
>>
>> Percentage of preempting and non-preempting context switches help
>> understanding the nature of workloads (CPU or IO bound) that are running
>> on a machine;
>>
>> The event is treated as preemption one when task->state value of the
>> thread being switched out is TASK_RUNNING. Event type encoding is
>> implemented using PERF_RECORD_MISC_SWITCH_OUT_PREEMPT bit;
>>
>> Signed-off-by: Alexey Budankov <alexey.budan...@linux.intel.com>
>
> Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
>
> Acme, I'm thinking you should route this, since most of the changes are
> actually to the tool.
>
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index fc1c330c6bd6..872a5aaa77eb 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -7584,6 +7584,10 @@ static void perf_event_switch(struct task_struct
>> *task,
>> },
>> };
>>
>> + if (!sched_in && task->state == TASK_RUNNING)
>> + switch_event.event_id.header.misc |=
>> + PERF_RECORD_MISC_SWITCH_OUT_PREEMPT;
>
> I typically prefer {} over any multi-line expression.
Yep, makes sense. Sorry for missing that here.
>
>> perf_iterate_sb(perf_event_switch_output,
>> &switch_event,
>> NULL);
>
