Messages in this thread | | | Date | Thu, 12 Dec 2019 14:42:31 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v8] perf: Sharing PMU counters across compatible events |
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On Fri, Dec 06, 2019 at 04:24:47PM -0800, Song Liu wrote: > +/* Remove dup_master for the event */ > +static void perf_event_remove_dup(struct perf_event *event, > + struct perf_event_context *ctx) > + > +{ > + struct perf_event *tmp, *new_master; > + int count; > + > + /* no sharing */ > + if (!event->dup_master) > + return; > + > + WARN_ON_ONCE(event->state != PERF_EVENT_STATE_INACTIVE && > + event->state != PERF_EVENT_STATE_OFF); > + > + /* this event is not the master */ > + if (event->dup_master != event) { > + event->dup_master = NULL; > + return; > + } > + > + /* this event is the master */ > + perf_event_exit_dup_master(event); > + > + count = 0; > + new_master = NULL; > + list_for_each_entry(tmp, &ctx->event_list, event_entry) { > + WARN_ON_ONCE(tmp->state > PERF_EVENT_STATE_INACTIVE); > + if (tmp->dup_master == event) { > + count++; > + if (!new_master) > + new_master = tmp; > + } > + } > + > + if (!count) > + return; > + > + if (count == 1) { > + /* no more sharing */ > + new_master->dup_master = NULL; > + return; > + } > + > + perf_event_init_dup_master(new_master); > + > + /* switch to new_master */ > + list_for_each_entry(tmp, &ctx->event_list, event_entry) > + if (tmp->dup_master == event) > + tmp->dup_master = new_master; > +}
I'm thinking you can do that in a single iteration:
list_for_each_entry(tmp, &ctx->event_list, event_entry) { if (tmp->dup_master != event) continue;
if (!new_master) new_master = tmp;
tmp->dup_master = new_master; count++; }
if (count == 1) new_master->dup_master = NULL; else perf_event_init_dup_master(new_master);
Hmm?
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