Hi Nilay,
Sounds good, I will post an updated version.
Thanks,
David
On Mon, Aug 8, 2016 at 9:12 AM, Nilay Vaish <nilayva...@gmail.com> wrote:
> On 7 August 2016 at 15:10, David Carrillo-Cisneros <davi...@google.com> wrote:
>> Hi Nilay,
>>
>>>> static int perf_event_read(struct perf_event *event, bool group)
>>>> {
>>>> - int ret = 0;
>>>> + int ret = 0, cpu_to_read;
>>>>
>>>> - /*
>>>> - * If event is enabled and currently active on a CPU, update the
>>>> - * value in the event structure:
>>>> - */
>>>> - if (event->state == PERF_EVENT_STATE_ACTIVE) {
>>>> + cpu_to_read = find_cpu_to_read(event);
>>>> +
>>>> + if (cpu_to_read >= 0) {
>>>> struct perf_read_data data = {
>>>> .event = event,
>>>> .group = group,
>>>> .ret = 0,
>>>> };
>>>> - ret = smp_call_function_single(event->oncpu,
>>>> + ret = smp_call_function_single(cpu_to_read,
>>>> __perf_event_read, &data,
>>>> 1);
>>>> ret = ret ? : data.ret;
>>>> } else if (event->state == PERF_EVENT_STATE_INACTIVE) {
>>>>
>>>
>>> I would like to suggest a small change to this patch. I think the check on
>>> PERF_EVENT_STATE_ACTIVE should be retained in the perf_event_read()
>>> function. The new function should assume that the event is active. I find
>>> this more readable since the next check in function perf_event_read() is on
>>> PERF_EVENT_STATE_INACTIVE.
>>
>> Two oncoming flags that Intel CQM/CMT will use are meant to allow read
>> even if event is inactive. This makes sense in CQM/CMT because the hw
>> RMID is always reserved. I am ok with keeping the check for
>> STATE_ACTIVE until those flags are actually introduced, tough.
>
>
> Hello David
>
> Lets go with checking PERF_EVENT_STATE_ACTIVE in perf_event_read() for
> the time being. With the new version of the patch that you posted, I
> find that checking PERF_EVENT_STATE_ACTIVE in find_cpu_to_read() makes
> you introduce another if statement for checking STATE_INACTIVE.
>
> If your CQM/CMT patches later need the code structure you have now, I
> would also support it. But as of now, I think, it is better to check
> STATE_ACTIVE in perf_event_read().
>
>
> Thanks
> Nilay
