Messages in this thread Patch in this message | | | Date | Tue, 21 Jul 2020 15:10:11 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH V6 11/14] perf/x86/intel: Disable sample-read the slots and metrics events |
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On Fri, Jul 17, 2020 at 07:05:51AM -0700, kan.liang@linux.intel.com wrote: > From: Kan Liang <kan.liang@linux.intel.com> > > Users fail to sample-read the slots and metrics events, e.g., > perf record -e '{slots, topdown-retiring}:S'. > > When reading the metrics event, the fixed counter 3 (slots) has to be > reset, which impacts the sampling of the slots event. > > Add a specific validate_group() support to reject the case and error out > for Ice Lake. > > An alternative fix may unconditionally disable slots sampling, but it's > not a decent fix. Users may want to only sample the slot events > without the topdown metrics events. > > Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
I'm confused by this; it doesn't make sense.
Should not patch 7 have something like the below instead?
Also, I think there is a bug when we create a group like this and then kill the leader, in that case the core code will 'promote' the sibling metric events to their own individual events, see perf_group_detach().
We need additional code to move those events into unrecoverable ERROR state. A new group_caps flag could indicate this promotion isn't allowed.
--- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3441,8 +3441,22 @@ static int intel_pmu_hw_config(struct pe * A flag PERF_X86_EVENT_TOPDOWN is applied for the case. */ if (x86_pmu.intel_cap.perf_metrics && is_topdown_event(event)) { - if (is_metric_event(event) && is_sampling_event(event)) - return -EINVAL; + + if (is_metric_event(event)) { + struct perf_event *leader = event->group_leader; + + if (is_sampling_event(event)) + return -EINVAL; + + if (leader == event) + return -EINVAL; + + if (!is_slots_event(leader)) + return -EINVAL; + + if (is_sampling_event(leader)) + return -EINVAL; + } if (!is_sampling_event(event)) { if (event->attr.config1 != 0)
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