On Mon, Feb 12, 2018 at 02:22:30PM -0800, Raghavendra Rao Ananta wrote: > > > On 02/12/2018 01:21 PM, Jiri Olsa wrote: > > On Mon, Feb 12, 2018 at 10:04:42PM +0100, Jiri Olsa wrote: > > > On Mon, Feb 12, 2018 at 09:42:05AM -0800, Raghavendra Rao Ananta wrote: > > > > Hi Jiri, > > > > > > > > Thank you for the response. > > > > > > > > Does perf tool has its own check to see if the CPU was offline during > > > > the > > > > lifetime of an event? If so, it might ignore these type of events. > > > > > > nope, we don't check on that > > > > > > > > > > > Initially, I tested the same using perf tool and found similar results. > > > > Then I debugged further and found that the perf core was actually > > > > sending > > > > data to the userspace (copy_to_user()) and the corresponding count for > > > > the > > > > data. Hence, I tested this further by writing my own userspace > > > > application, > > > > and I was able to read the count through this, > > > > even when the CPU was made offline and back online. > > > > > > > > Do you think we also have to modify the perf tool accordingly? > > > > > > hum, I wonder what's wrong.. will check > > > > I think the user space needs to enable the event once the > > cpu gets online.. which we dont do and your app does..? > > > > maybe we could add perf_event_attr::enable_on_online ;-) > > > > I'll check what we can do in user space, I guess we can > > monitor the cpu state and enable event accordingly > > > > jirka > > > Yes, probably that's the reason. > > In order for an event to get scheduled-in, it expects the event to be at > least in PERF_EVENT_STATE_INACTIVE state. If you notice, in my patch, > when the cpu wakes up, we are initializing the state of the event > (perf_event__state_init()) and then trying to schedule-in. Since the event > was created with a disabled state, it seems that the same this is followed > and the state gets initialized to PERF_EVENT_STATE_OFF. Unfortunately, > events in this state could not be scheduled. > > One way for things to get working is, instead of calling > perf_event__state_init() before the event is scheduled-in (when the cpu > wakes up), we can do something like: > perf_event_set_state(event, PERF_EVENT_STATE_INACTIVE);
could you add check in ioctl call that set the inactive state on the dormant event.. that would start it once the cpu is online.. as requested jirka
