Messages in this thread | | | Date | Mon, 30 Sep 2019 16:07:55 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH V4 07/14] perf/x86/intel: Support hardware TopDown metrics |
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On Mon, Sep 30, 2019 at 03:06:15PM +0200, Peter Zijlstra wrote: > On Mon, Sep 16, 2019 at 06:41:21AM -0700, kan.liang@linux.intel.com wrote:
> > +static bool is_first_topdown_event_in_group(struct perf_event *event) > > +{ > > + struct perf_event *first = NULL; > > + > > + if (is_topdown_event(event->group_leader)) > > + first = event->group_leader; > > + else { > > + for_each_sibling_event(first, event->group_leader) > > + if (is_topdown_event(first)) > > + break; > > + } > > + > > + if (event == first) > > + return true; > > + > > + return false; > > +} > > > +static u64 icl_update_topdown_event(struct perf_event *event) > > +{ > > + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); > > + struct perf_event *other; > > + u64 slots, metrics; > > + int idx; > > + > > + /* > > + * Only need to update all events for the first > > + * slots/metrics event in a group > > + */ > > + if (event && !is_first_topdown_event_in_group(event)) > > + return 0; > > This is pretty crap and approaches O(n^2); let me think if there's > anything saner to do here.
This is also really complicated in the case where we do perf_remove_from_context() in the 'wrong' order.
In that case we get detached events that are not up-to-date (and never will be). It doesn't look like that matters, but it is weird.
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