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perf/x86/intel: Remove intel_excl_states::init_state 

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>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-05-21 10:57:39 +02:00 committed by Ingo Molnar
parent 1fe684e349
commit 43ef205bde
3 changed files with 2 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/kernel/cpu/perf_event.c
View File

@ -884,7 +884,6 @@ int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
}
if (!assign || unsched) {
for (i = 0; i < n; i++) {
e = cpuc->event_list[i];
/*

1
arch/x86/kernel/cpu/perf_event.h
View File

@ -133,7 +133,6 @@ 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 */
};

22
arch/x86/kernel/cpu/perf_event_intel.c
View File

@ -1927,11 +1927,6 @@ intel_start_scheduling(struct cpu_hw_events *cpuc)
* 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(struct cpu_hw_events *cpuc, int idx, int cnt
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_events *cpuc)
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())
@ -2519,19 +2509,11 @@ struct intel_shared_regs *allocate_shared_regs(int cpu)
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;