[PATCH 4/4] perf: Convert perf_event to local_t

From: Peter Zijlstra
Date: Fri May 21 2010 - 10:21:15 EST

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Since now all modification to event->count (and ->prev_count
and ->period_left) are local to a cpu, change then to local64_t so we
avoid the LOCK'ed ops.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
LKML-Reference: <new-submission>
---
arch/arm/kernel/perf_event.c | 18 ++++++++--------
arch/powerpc/kernel/perf_event.c | 34 +++++++++++++++----------------
arch/sh/kernel/perf_event.c | 6 ++---
arch/sparc/kernel/perf_event.c | 18 ++++++++--------
arch/x86/kernel/cpu/perf_event.c | 18 ++++++++--------
include/linux/perf_event.h | 7 +++---
kernel/perf_event.c | 42 +++++++++++++++++++--------------------
7 files changed, 72 insertions(+), 71 deletions(-)

Index: linux-2.6/arch/arm/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/arch/arm/kernel/perf_event.c
+++ linux-2.6/arch/arm/kernel/perf_event.c
@@ -128,20 +128,20 @@ armpmu_event_set_period(struct perf_even
struct hw_perf_event *hwc,
int idx)
{
- s64 left = atomic64_read(&hwc->period_left);
+ s64 left = local64_read(&hwc->period_left);
s64 period = hwc->sample_period;
int ret = 0;

if (unlikely(left <= -period)) {
left = period;
- atomic64_set(&hwc->period_left, left);
+ local64_set(&hwc->period_left, left);
hwc->last_period = period;
ret = 1;
}

if (unlikely(left <= 0)) {
left += period;
- atomic64_set(&hwc->period_left, left);
+ local64_set(&hwc->period_left, left);
hwc->last_period = period;
ret = 1;
}
@@ -149,7 +149,7 @@ armpmu_event_set_period(struct perf_even
if (left > (s64)armpmu->max_period)
left = armpmu->max_period;

- atomic64_set(&hwc->prev_count, (u64)-left);
+ local64_set(&hwc->prev_count, (u64)-left);

armpmu->write_counter(idx, (u64)(-left) & 0xffffffff);

@@ -168,18 +168,18 @@ armpmu_event_update(struct perf_event *e
s64 delta;

again:
- prev_raw_count = atomic64_read(&hwc->prev_count);
+ prev_raw_count = local64_read(&hwc->prev_count);
new_raw_count = armpmu->read_counter(idx);

- if (atomic64_cmpxchg(&hwc->prev_count, prev_raw_count,
+ if (local64_cmpxchg(&hwc->prev_count, prev_raw_count,
new_raw_count) != prev_raw_count)
goto again;

delta = (new_raw_count << shift) - (prev_raw_count << shift);
delta >>= shift;

- atomic64_add(delta, &event->count);
- atomic64_sub(delta, &hwc->period_left);
+ local64_add(delta, &event->count);
+ local64_sub(delta, &hwc->period_left);

return new_raw_count;
}
@@ -433,7 +433,7 @@ __hw_perf_event_init(struct perf_event *
if (!hwc->sample_period) {
hwc->sample_period = armpmu->max_period;
hwc->last_period = hwc->sample_period;
- atomic64_set(&hwc->period_left, hwc->sample_period);
+ local64_set(&hwc->period_left, hwc->sample_period);
}

err = 0;
Index: linux-2.6/arch/powerpc/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/arch/powerpc/kernel/perf_event.c
+++ linux-2.6/arch/powerpc/kernel/perf_event.c
@@ -410,15 +410,15 @@ static void power_pmu_read(struct perf_e
* Therefore we treat them like NMIs.
*/
do {
- prev = atomic64_read(&event->hw.prev_count);
+ prev = local64_read(&event->hw.prev_count);
barrier();
val = read_pmc(event->hw.idx);
- } while (atomic64_cmpxchg(&event->hw.prev_count, prev, val) != prev);
+ } while (local64_cmpxchg(&event->hw.prev_count, prev, val) != prev);

/* The counters are only 32 bits wide */
delta = (val - prev) & 0xfffffffful;
- atomic64_add(delta, &event->count);
- atomic64_sub(delta, &event->hw.period_left);
+ local64_add(delta, &event->count);
+ local64_sub(delta, &event->hw.period_left);
}

/*
@@ -444,10 +444,10 @@ static void freeze_limited_counters(stru
if (!event->hw.idx)
continue;
val = (event->hw.idx == 5) ? pmc5 : pmc6;
- prev = atomic64_read(&event->hw.prev_count);
+ prev = local64_read(&event->hw.prev_count);
event->hw.idx = 0;
delta = (val - prev) & 0xfffffffful;
- atomic64_add(delta, &event->count);
+ local64_add(delta, &event->count);
}
}

@@ -462,7 +462,7 @@ static void thaw_limited_counters(struct
event = cpuhw->limited_counter[i];
event->hw.idx = cpuhw->limited_hwidx[i];
val = (event->hw.idx == 5) ? pmc5 : pmc6;
- atomic64_set(&event->hw.prev_count, val);
+ local64_set(&event->hw.prev_count, val);
perf_event_update_userpage(event);
}
}
@@ -666,11 +666,11 @@ void hw_perf_enable(void)
}
val = 0;
if (event->hw.sample_period) {
- left = atomic64_read(&event->hw.period_left);
+ left = local64_read(&event->hw.period_left);
if (left < 0x80000000L)
val = 0x80000000L - left;
}
- atomic64_set(&event->hw.prev_count, val);
+ local64_set(&event->hw.prev_count, val);
event->hw.idx = idx;
write_pmc(idx, val);
perf_event_update_userpage(event);
@@ -842,8 +842,8 @@ static void power_pmu_unthrottle(struct
if (left < 0x80000000L)
val = 0x80000000L - left;
write_pmc(event->hw.idx, val);
- atomic64_set(&event->hw.prev_count, val);
- atomic64_set(&event->hw.period_left, left);
+ local64_set(&event->hw.prev_count, val);
+ local64_set(&event->hw.period_left, left);
perf_event_update_userpage(event);
perf_enable();
local_irq_restore(flags);
@@ -1108,7 +1108,7 @@ const struct pmu *hw_perf_event_init(str
event->hw.config = events[n];
event->hw.event_base = cflags[n];
event->hw.last_period = event->hw.sample_period;
- atomic64_set(&event->hw.period_left, event->hw.last_period);
+ local64_set(&event->hw.period_left, event->hw.last_period);

/*
* See if we need to reserve the PMU.
@@ -1146,16 +1146,16 @@ static void record_and_restart(struct pe
int record = 0;

/* we don't have to worry about interrupts here */
- prev = atomic64_read(&event->hw.prev_count);
+ prev = local64_read(&event->hw.prev_count);
delta = (val - prev) & 0xfffffffful;
- atomic64_add(delta, &event->count);
+ local64_add(delta, &event->count);

/*
* See if the total period for this event has expired,
* and update for the next period.
*/
val = 0;
- left = atomic64_read(&event->hw.period_left) - delta;
+ left = local64_read(&event->hw.period_left) - delta;
if (period) {
if (left <= 0) {
left += period;
@@ -1193,8 +1193,8 @@ static void record_and_restart(struct pe
}

write_pmc(event->hw.idx, val);
- atomic64_set(&event->hw.prev_count, val);
- atomic64_set(&event->hw.period_left, left);
+ local64_set(&event->hw.prev_count, val);
+ local64_set(&event->hw.period_left, left);
perf_event_update_userpage(event);
}

Index: linux-2.6/arch/sh/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/arch/sh/kernel/perf_event.c
+++ linux-2.6/arch/sh/kernel/perf_event.c
@@ -185,10 +185,10 @@ static void sh_perf_event_update(struct
* this is the simplest approach for maintaining consistency.
*/
again:
- prev_raw_count = atomic64_read(&hwc->prev_count);
+ prev_raw_count = local64_read(&hwc->prev_count);
new_raw_count = sh_pmu->read(idx);

- if (atomic64_cmpxchg(&hwc->prev_count, prev_raw_count,
+ if (local64_cmpxchg(&hwc->prev_count, prev_raw_count,
new_raw_count) != prev_raw_count)
goto again;

@@ -203,7 +203,7 @@ again:
delta = (new_raw_count << shift) - (prev_raw_count << shift);
delta >>= shift;

- atomic64_add(delta, &event->count);
+ local64_add(delta, &event->count);
}

static void sh_pmu_disable(struct perf_event *event)
Index: linux-2.6/arch/sparc/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/arch/sparc/kernel/perf_event.c
+++ linux-2.6/arch/sparc/kernel/perf_event.c
@@ -571,18 +571,18 @@ static u64 sparc_perf_event_update(struc
s64 delta;

again:
- prev_raw_count = atomic64_read(&hwc->prev_count);
+ prev_raw_count = local64_read(&hwc->prev_count);
new_raw_count = read_pmc(idx);

- if (atomic64_cmpxchg(&hwc->prev_count, prev_raw_count,
+ if (local64_cmpxchg(&hwc->prev_count, prev_raw_count,
new_raw_count) != prev_raw_count)
goto again;

delta = (new_raw_count << shift) - (prev_raw_count << shift);
delta >>= shift;

- atomic64_add(delta, &event->count);
- atomic64_sub(delta, &hwc->period_left);
+ local64_add(delta, &event->count);
+ local64_sub(delta, &hwc->period_left);

return new_raw_count;
}
@@ -590,27 +590,27 @@ again:
static int sparc_perf_event_set_period(struct perf_event *event,
struct hw_perf_event *hwc, int idx)
{
- s64 left = atomic64_read(&hwc->period_left);
+ s64 left = local64_read(&hwc->period_left);
s64 period = hwc->sample_period;
int ret = 0;

if (unlikely(left <= -period)) {
left = period;
- atomic64_set(&hwc->period_left, left);
+ local64_set(&hwc->period_left, left);
hwc->last_period = period;
ret = 1;
}

if (unlikely(left <= 0)) {
left += period;
- atomic64_set(&hwc->period_left, left);
+ local64_set(&hwc->period_left, left);
hwc->last_period = period;
ret = 1;
}
if (left > MAX_PERIOD)
left = MAX_PERIOD;

- atomic64_set(&hwc->prev_count, (u64)-left);
+ local64_set(&hwc->prev_count, (u64)-left);

write_pmc(idx, (u64)(-left) & 0xffffffff);

@@ -1086,7 +1086,7 @@ static int __hw_perf_event_init(struct p
if (!hwc->sample_period) {
hwc->sample_period = MAX_PERIOD;
hwc->last_period = hwc->sample_period;
- atomic64_set(&hwc->period_left, hwc->sample_period);
+ local64_set(&hwc->period_left, hwc->sample_period);
}

return 0;
Index: linux-2.6/arch/x86/kernel/cpu/perf_event.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event.c
@@ -294,10 +294,10 @@ x86_perf_event_update(struct perf_event
* count to the generic event atomically:
*/
again:
- prev_raw_count = atomic64_read(&hwc->prev_count);
+ prev_raw_count = local64_read(&hwc->prev_count);
rdmsrl(hwc->event_base + idx, new_raw_count);

- if (atomic64_cmpxchg(&hwc->prev_count, prev_raw_count,
+ if (local64_cmpxchg(&hwc->prev_count, prev_raw_count,
new_raw_count) != prev_raw_count)
goto again;

@@ -312,8 +312,8 @@ again:
delta = (new_raw_count << shift) - (prev_raw_count << shift);
delta >>= shift;

- atomic64_add(delta, &event->count);
- atomic64_sub(delta, &hwc->period_left);
+ local64_add(delta, &event->count);
+ local64_sub(delta, &hwc->period_left);

return new_raw_count;
}
@@ -437,7 +437,7 @@ static int x86_setup_perfctr(struct perf
if (!hwc->sample_period) {
hwc->sample_period = x86_pmu.max_period;
hwc->last_period = hwc->sample_period;
- atomic64_set(&hwc->period_left, hwc->sample_period);
+ local64_set(&hwc->period_left, hwc->sample_period);
} else {
/*
* If we have a PMU initialized but no APIC
@@ -884,7 +884,7 @@ static int
x86_perf_event_set_period(struct perf_event *event)
{
struct hw_perf_event *hwc = &event->hw;
- s64 left = atomic64_read(&hwc->period_left);
+ s64 left = local64_read(&hwc->period_left);
s64 period = hwc->sample_period;
int ret = 0, idx = hwc->idx;

@@ -896,14 +896,14 @@ x86_perf_event_set_period(struct perf_ev
*/
if (unlikely(left <= -period)) {
left = period;
- atomic64_set(&hwc->period_left, left);
+ local64_set(&hwc->period_left, left);
hwc->last_period = period;
ret = 1;
}

if (unlikely(left <= 0)) {
left += period;
- atomic64_set(&hwc->period_left, left);
+ local64_set(&hwc->period_left, left);
hwc->last_period = period;
ret = 1;
}
@@ -922,7 +922,7 @@ x86_perf_event_set_period(struct perf_ev
* The hw event starts counting from this event offset,
* mark it to be able to extra future deltas:
*/
- atomic64_set(&hwc->prev_count, (u64)-left);
+ local64_set(&hwc->prev_count, (u64)-left);

wrmsrl(hwc->event_base + idx,
(u64)(-left) & x86_pmu.cntval_mask);
Index: linux-2.6/include/linux/perf_event.h
===================================================================
--- linux-2.6.orig/include/linux/perf_event.h
+++ linux-2.6/include/linux/perf_event.h
@@ -486,6 +486,7 @@ struct perf_guest_info_callbacks {
#include <linux/cpu.h>
#include <asm/atomic.h>
#include <asm/local.h>
+#include <asm/local64.h>

#define PERF_MAX_STACK_DEPTH 255

@@ -535,10 +536,10 @@ struct hw_perf_event {
struct arch_hw_breakpoint info;
#endif
};
- atomic64_t prev_count;
+ local64_t prev_count;
u64 sample_period;
u64 last_period;
- atomic64_t period_left;
+ local64_t period_left;
u64 interrupts;

u64 freq_time_stamp;
@@ -647,7 +648,7 @@ struct perf_event {
const struct pmu *pmu;

enum perf_event_active_state state;
- atomic64_t count;
+ local64_t count;
atomic64_t child_count;

/*
Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -1116,9 +1116,9 @@ static void __perf_event_sync_stat(struc
* In order to keep per-task stats reliable we need to flip the event
* values when we flip the contexts.
*/
- value = atomic64_read(&next_event->count);
- value = atomic64_xchg(&event->count, value);
- atomic64_set(&next_event->count, value);
+ value = local64_read(&next_event->count);
+ value = local64_xchg(&event->count, value);
+ local64_set(&next_event->count, value);

swap(event->total_time_enabled, next_event->total_time_enabled);
swap(event->total_time_running, next_event->total_time_running);
@@ -1505,10 +1505,10 @@ static void perf_adjust_period(struct pe

hwc->sample_period = sample_period;

- if (atomic64_read(&hwc->period_left) > 8*sample_period) {
+ if (local64_read(&hwc->period_left) > 8*sample_period) {
perf_disable();
perf_event_stop(event);
- atomic64_set(&hwc->period_left, 0);
+ local64_set(&hwc->period_left, 0);
perf_event_start(event);
perf_enable();
}
@@ -1549,7 +1549,7 @@ static void perf_ctx_adjust_freq(struct

perf_disable();
event->pmu->read(event);
- now = atomic64_read(&event->count);
+ now = local64_read(&event->count);
delta = now - hwc->freq_count_stamp;
hwc->freq_count_stamp = now;

@@ -1703,7 +1703,7 @@ static void __perf_event_read(void *info

static inline u64 perf_event_count(struct perf_event *event)
{
- return atomic64_read(&event->count) + atomic64_read(&event->child_count);
+ return local64_read(&event->count) + atomic64_read(&event->child_count);
}

static u64 perf_event_read(struct perf_event *event)
@@ -2105,7 +2105,7 @@ static unsigned int perf_poll(struct fil
static void perf_event_reset(struct perf_event *event)
{
(void)perf_event_read(event);
- atomic64_set(&event->count, 0);
+ local64_set(&event->count, 0);
perf_event_update_userpage(event);
}

@@ -2287,7 +2287,7 @@ void perf_event_update_userpage(struct p
userpg->index = perf_event_index(event);
userpg->offset = perf_event_count(event);
if (event->state == PERF_EVENT_STATE_ACTIVE)
- userpg->offset -= atomic64_read(&event->hw.prev_count);
+ userpg->offset -= local64_read(&event->hw.prev_count);

userpg->time_enabled = event->total_time_enabled +
atomic64_read(&event->child_total_time_enabled);
@@ -3937,14 +3937,14 @@ static u64 perf_swevent_set_period(struc
hwc->last_period = hwc->sample_period;

again:
- old = val = atomic64_read(&hwc->period_left);
+ old = val = local64_read(&hwc->period_left);
if (val < 0)
return 0;

nr = div64_u64(period + val, period);
offset = nr * period;
val -= offset;
- if (atomic64_cmpxchg(&hwc->period_left, old, val) != old)
+ if (local64_cmpxchg(&hwc->period_left, old, val) != old)
goto again;

return nr;
@@ -3990,7 +3990,7 @@ static void perf_swevent_add(struct perf
{
struct hw_perf_event *hwc = &event->hw;

- atomic64_add(nr, &event->count);
+ local64_add(nr, &event->count);

if (!regs)
return;
@@ -4001,7 +4001,7 @@ static void perf_swevent_add(struct perf
if (nr == 1 && hwc->sample_period == 1 && !event->attr.freq)
return perf_swevent_overflow(event, 1, nmi, data, regs);

- if (atomic64_add_negative(nr, &hwc->period_left))
+ if (local64_add_negative(nr, &hwc->period_left))
return;

perf_swevent_overflow(event, 0, nmi, data, regs);
@@ -4283,8 +4283,8 @@ static void cpu_clock_perf_event_update(
u64 now;

now = cpu_clock(cpu);
- prev = atomic64_xchg(&event->hw.prev_count, now);
- atomic64_add(now - prev, &event->count);
+ prev = local64_xchg(&event->hw.prev_count, now);
+ local64_add(now - prev, &event->count);
}

static int cpu_clock_perf_event_enable(struct perf_event *event)
@@ -4292,7 +4292,7 @@ static int cpu_clock_perf_event_enable(s
struct hw_perf_event *hwc = &event->hw;
int cpu = raw_smp_processor_id();

- atomic64_set(&hwc->prev_count, cpu_clock(cpu));
+ local64_set(&hwc->prev_count, cpu_clock(cpu));
perf_swevent_start_hrtimer(event);

return 0;
@@ -4324,9 +4324,9 @@ static void task_clock_perf_event_update
u64 prev;
s64 delta;

- prev = atomic64_xchg(&event->hw.prev_count, now);
+ prev = local64_xchg(&event->hw.prev_count, now);
delta = now - prev;
- atomic64_add(delta, &event->count);
+ local64_add(delta, &event->count);
}

static int task_clock_perf_event_enable(struct perf_event *event)
@@ -4336,7 +4336,7 @@ static int task_clock_perf_event_enable(

now = event->ctx->time;

- atomic64_set(&hwc->prev_count, now);
+ local64_set(&hwc->prev_count, now);

perf_swevent_start_hrtimer(event);

@@ -4777,7 +4777,7 @@ perf_event_alloc(struct perf_event_attr
hwc->sample_period = 1;
hwc->last_period = hwc->sample_period;

- atomic64_set(&hwc->period_left, hwc->sample_period);
+ local64_set(&hwc->period_left, hwc->sample_period);

/*
* we currently do not support PERF_FORMAT_GROUP on inherited events
@@ -5216,7 +5216,7 @@ inherit_event(struct perf_event *parent_
hwc->sample_period = sample_period;
hwc->last_period = sample_period;

- atomic64_set(&hwc->period_left, sample_period);
+ local64_set(&hwc->period_left, sample_period);
}

child_event->overflow_handler = parent_event->overflow_handler;

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