[PATCH v2 09/11] perf/x86: Remove intel_excl_states::init_state

[Peter Zijlstra <peterz@infradead.org>]

[-- Attachment #1: peterz-pmu-sched-8.patch --]
[-- Type: text/plain, Size: 3178 bytes --]

For some obscure reason intel_{start,stop}_scheduling() copy the HT
state to an intermediate array. This would make sense if we ever were
to make changes to it which we'd have to discard.

Except we don't. By the time we call intel_commit_scheduling() we're;
as the name implies; committed to them. We'll never back out.

A further hint its pointless is that stop_scheduling() unconditionally
publishes the state.

So the intermediate array is pointless, modify the state in place and
kill the extra array.

And remove the pointless array initialization: INTEL_EXCL_UNUSED == 0.

Note; all is serialized by intel_excl_cntr::lock.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/kernel/cpu/perf_event.c       |    1 -
 arch/x86/kernel/cpu/perf_event.h       |    1 -
 arch/x86/kernel/cpu/perf_event_intel.c |   22 ++--------------------
 3 files changed, 2 insertions(+), 22 deletions(-)

--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -861,7 +861,6 @@ int x86_schedule_events(struct cpu_hw_ev
 	}
 
 	if (!assign || unsched) {
-
 		for (i = 0; i < n; i++) {
 			e = cpuc->event_list[i];
 			/*
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -132,7 +132,6 @@ enum intel_excl_state_type {
 };
 
 struct intel_excl_states {
-	enum intel_excl_state_type init_state[X86_PMC_IDX_MAX];
 	enum intel_excl_state_type state[X86_PMC_IDX_MAX];
 	bool sched_started; /* true if scheduling has started */
 };
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1927,11 +1927,6 @@ intel_start_scheduling(struct cpu_hw_eve
 	 * makes scheduling appear as a transaction
 	 */
 	raw_spin_lock(&excl_cntrs->lock);
-
-	/*
-	 * Save a copy of our state to work on.
-	 */
-	memcpy(xl->init_state, xl->state, sizeof(xl->init_state));
 }
 
 static void intel_commit_scheduling(struct cpu_hw_events *cpuc, int idx, int cntr)
@@ -1955,9 +1950,9 @@ static void intel_commit_scheduling(stru
 	lockdep_assert_held(&excl_cntrs->lock);
 
 	if (c->flags & PERF_X86_EVENT_EXCL)
-		xl->init_state[cntr] = INTEL_EXCL_EXCLUSIVE;
+		xl->state[cntr] = INTEL_EXCL_EXCLUSIVE;
 	else
-		xl->init_state[cntr] = INTEL_EXCL_SHARED;
+		xl->state[cntr] = INTEL_EXCL_SHARED;
 }
 
 static void
@@ -1980,11 +1975,6 @@ intel_stop_scheduling(struct cpu_hw_even
 
 	xl = &excl_cntrs->states[tid];
 
-	/*
-	 * Commit the working state.
-	 */
-	memcpy(xl->state, xl->init_state, sizeof(xl->state));
-
 	xl->sched_started = false;
 	/*
 	 * release shared state lock (acquired in intel_start_scheduling())
@@ -2509,19 +2499,11 @@ struct intel_shared_regs *allocate_share
 static struct intel_excl_cntrs *allocate_excl_cntrs(int cpu)
 {
 	struct intel_excl_cntrs *c;
-	int i;
 
 	c = kzalloc_node(sizeof(struct intel_excl_cntrs),
 			 GFP_KERNEL, cpu_to_node(cpu));
 	if (c) {
 		raw_spin_lock_init(&c->lock);
-		for (i = 0; i < X86_PMC_IDX_MAX; i++) {
-			c->states[0].state[i] = INTEL_EXCL_UNUSED;
-			c->states[0].init_state[i] = INTEL_EXCL_UNUSED;
-
-			c->states[1].state[i] = INTEL_EXCL_UNUSED;
-			c->states[1].init_state[i] = INTEL_EXCL_UNUSED;
-		}
 		c->core_id = -1;
 	}
 	return c;