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perf/core: Add a new PERF_EV_CAP_SIBLING event capability
Current perf assumes that events in a group are independent. Close an event doesn't impact the value of the other events in the same group. If the closed event is a member, after the event closure, other events are still running like a group. If the closed event is a leader, other events are running as singleton events. Add PERF_EV_CAP_SIBLING to allow events to indicate they require being part of a group, and when the leader dies they cannot exist independently. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200723171117.9918-8-kan.liang@linux.intel.com
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@ -576,9 +576,13 @@ typedef void (*perf_overflow_handler_t)(struct perf_event *,
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* PERF_EV_CAP_SOFTWARE: Is a software event.
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* PERF_EV_CAP_READ_ACTIVE_PKG: A CPU event (or cgroup event) that can be read
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* from any CPU in the package where it is active.
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* PERF_EV_CAP_SIBLING: An event with this flag must be a group sibling and
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* cannot be a group leader. If an event with this flag is detached from the
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* group it is scheduled out and moved into an unrecoverable ERROR state.
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*/
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#define PERF_EV_CAP_SOFTWARE BIT(0)
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#define PERF_EV_CAP_READ_ACTIVE_PKG BIT(1)
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#define PERF_EV_CAP_SIBLING BIT(2)
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#define SWEVENT_HLIST_BITS 8
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#define SWEVENT_HLIST_SIZE (1 << SWEVENT_HLIST_BITS)
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@ -2133,8 +2133,24 @@ static inline struct list_head *get_event_list(struct perf_event *event)
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return event->attr.pinned ? &ctx->pinned_active : &ctx->flexible_active;
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}
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/*
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* Events that have PERF_EV_CAP_SIBLING require being part of a group and
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* cannot exist on their own, schedule them out and move them into the ERROR
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* state. Also see _perf_event_enable(), it will not be able to recover
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* this ERROR state.
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*/
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static inline void perf_remove_sibling_event(struct perf_event *event)
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{
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struct perf_event_context *ctx = event->ctx;
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struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
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event_sched_out(event, cpuctx, ctx);
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perf_event_set_state(event, PERF_EVENT_STATE_ERROR);
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}
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static void perf_group_detach(struct perf_event *event)
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{
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struct perf_event *leader = event->group_leader;
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struct perf_event *sibling, *tmp;
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struct perf_event_context *ctx = event->ctx;
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@ -2153,7 +2169,7 @@ static void perf_group_detach(struct perf_event *event)
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/*
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* If this is a sibling, remove it from its group.
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*/
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if (event->group_leader != event) {
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if (leader != event) {
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list_del_init(&event->sibling_list);
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event->group_leader->nr_siblings--;
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goto out;
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@ -2166,6 +2182,9 @@ static void perf_group_detach(struct perf_event *event)
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*/
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list_for_each_entry_safe(sibling, tmp, &event->sibling_list, sibling_list) {
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if (sibling->event_caps & PERF_EV_CAP_SIBLING)
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perf_remove_sibling_event(sibling);
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sibling->group_leader = sibling;
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list_del_init(&sibling->sibling_list);
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@ -2183,10 +2202,10 @@ static void perf_group_detach(struct perf_event *event)
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}
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out:
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perf_event__header_size(event->group_leader);
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for_each_sibling_event(tmp, event->group_leader)
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for_each_sibling_event(tmp, leader)
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perf_event__header_size(tmp);
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perf_event__header_size(leader);
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}
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static bool is_orphaned_event(struct perf_event *event)
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@ -2979,6 +2998,7 @@ static void _perf_event_enable(struct perf_event *event)
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raw_spin_lock_irq(&ctx->lock);
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if (event->state >= PERF_EVENT_STATE_INACTIVE ||
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event->state < PERF_EVENT_STATE_ERROR) {
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out:
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raw_spin_unlock_irq(&ctx->lock);
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return;
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}
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@ -2990,8 +3010,16 @@ static void _perf_event_enable(struct perf_event *event)
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* has gone back into error state, as distinct from the task having
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* been scheduled away before the cross-call arrived.
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*/
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if (event->state == PERF_EVENT_STATE_ERROR)
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if (event->state == PERF_EVENT_STATE_ERROR) {
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/*
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* Detached SIBLING events cannot leave ERROR state.
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*/
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if (event->event_caps & PERF_EV_CAP_SIBLING &&
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event->group_leader == event)
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goto out;
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event->state = PERF_EVENT_STATE_OFF;
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}
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raw_spin_unlock_irq(&ctx->lock);
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event_function_call(event, __perf_event_enable, NULL);
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