On 12/19/2017 3:08 PM, Liang, Kan wrote:
On 12/19/2017 1:58 PM, Peter Zijlstra wrote:
On Mon, Dec 18, 2017 at 03:34:49AM -0800, [email protected]
wrote:
arch/x86/events/core.c | 14 ++++++++++++++
arch/x86/events/intel/ds.c | 8 +++++++-
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 35552ea..f74e21d 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -100,6 +100,20 @@ u64 x86_perf_event_update(struct perf_event *event,
* of the count.
*/
delta = (new_raw_count << shift) - (prev_raw_count << shift);
+
+ /*
+ * Take auto-reload into account
+ * For the auto-reload before the last time, it went through the
+ * whole period (reload_val) every time.
+ * Just simply add period * times to the event.
+ *
+ * For the last load, the elapsed delta (event-)time need to be
+ * corrected by adding the period. Because the start point is
-period.
+ */
+ if (reload_times > 0) {
+ delta += (reload_val << shift);
+ local64_add(reload_val * (reload_times - 1), &event->count);
+ }
delta >>= shift;
local64_add(delta, &event->count);
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 0b693b7..f0f6026 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1256,11 +1256,17 @@ static void __intel_pmu_pebs_event(struct
perf_event *event,
void *base, void *top,
int bit, int count)
{
+ struct hw_perf_event *hwc = &event->hw;
struct perf_sample_data data;
struct pt_regs regs;
void *at = get_next_pebs_record_by_bit(base, top, bit);
- if (!intel_pmu_save_and_restart(event, 0, 0) &&
+ /*
+ * Now, auto-reload is only enabled in fixed period mode.
+ * The reload value is always hwc->sample_period.
+ * May need to change it, if auto-reload is enabled in freq mode
later.
+ */
+ if (!intel_pmu_save_and_restart(event, hwc->sample_period, count
- 1) &&
!(event->hw.flags & PERF_X86_EVENT_AUTO_RELOAD))
return;
This all looks very wrong... In auto reload we should never call
intel_pmu_save_and_restore() in the first place I think.
Things like x86_perf_event_update() and x86_perf_event_set_period()
simply _cannot_ do the right thing when we auto reload the counter.
I think it should be OK to call it in first place.
For x86_perf_event_update(), the reload_times will tell if it's auto
reload. Both period_left and event->count are carefully recalculated for
auto reload.
Think a bit more. You are right. We cannot rely on count to tell us if
it's auto reload.
The count could also be 1 if auto reload is enabled.
I will fix it in V2.
Thanks,
Kan
For x86_perf_event_set_period(), there is nothing special needed for
auto reload. The period is fixed. The period_left from
x86_perf_event_update() is already handled.
BTW: It should be 'count' not 'count - 1' which pass to
intel_pmu_save_and_restart(). I just found the issue. I will fix it in
V2 with other improvements if there are any.
Thanks,
Kan
