Messages in this thread | | | Subject | Re: [PATCH 3/3] events: Ensure that timers are updated without requiring read() call | From | Peter Zijlstra <> | Date | Fri, 24 Jun 2011 11:44:16 +0200 |
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On Thu, 2011-06-23 at 16:34 -0400, Eric B Munson wrote: > The event tracing infrastructure exposes two timers which should be updated > each time the value of the counter is updated. Currently, these counters are > only updated when userspace calls read() on the fd associated with an event. > This means that counters which are read via the mmap'd page exclusively never > have their timers updated. This patch adds ensures that the timers are updated > each time the values in the mmap'd page are updated. > > Signed-off-by: Eric B Munson <emunson@mgebm.net> > --- > kernel/events/core.c | 12 ++++++++++++ > 1 files changed, 12 insertions(+), 0 deletions(-) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 9e9a7fa..e3be175 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -3382,6 +3382,18 @@ void perf_event_update_userpage(struct perf_event *event) > struct perf_buffer *buffer; > > rcu_read_lock(); > + /* > + * compute total_time_enabled, total_time_running > + * based on snapshot values taken when the event > + * was last scheduled in. > + * > + * we cannot simply called update_context_time() > + * because of locking issue as we are called in
s/are/can be/
> + * NMI context > + */ > + calc_timer_values(event, > + &event->total_time_enabled, > + &event->total_time_running);
I'm not sure writing those from NMI context is a sane thing to do, best is to compute the values into a local variable and use that variable below.
Took the first two patches.
> buffer = rcu_dereference(event->buffer); > if (!buffer) > goto unlock;
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