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perf: Undo the per cpu-context timer stuff 

Revert the timer per cpu-context timers because of unfortunate
nohz interaction. Fixing that would have been somewhat ugly, so
go back to driving things from the regular tick. Provide a
jiffies interval feature for people who want slower rotations.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <20100917093009.519845633@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-09-17 11:28:50 +02:00 committed by Ingo Molnar
parent 917bdd1c9b
commit e9d2b06414
3 changed files with 56 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/perf_event.h
View File

@ -870,8 +870,8 @@ struct perf_cpu_context {
struct perf_event_context *task_ctx;
int active_oncpu;
int exclusive;
u64 timer_interval;
struct hrtimer timer;
struct list_head rotation_list;
int jiffies_interval;
};
struct perf_output_handle {
@ -1065,6 +1065,7 @@ extern int perf_swevent_get_recursion_context(void);
extern void perf_swevent_put_recursion_context(int rctx);
extern void perf_event_enable(struct perf_event *event);
extern void perf_event_disable(struct perf_event *event);
extern void perf_event_task_tick(void);
#else
static inline void
perf_event_task_sched_in(struct task_struct *task) { }
@ -1099,6 +1100,7 @@ static inline int perf_swevent_get_recursion_context(void) { return -1; }
static inline void perf_swevent_put_recursion_context(int rctx) { }
static inline void perf_event_enable(struct perf_event *event) { }
static inline void perf_event_disable(struct perf_event *event) { }
static inline void perf_event_task_tick(void) { }
#endif
#define perf_output_put(handle, x) \

81
kernel/perf_event.c
View File

@ -77,23 +77,22 @@ void perf_pmu_enable(struct pmu *pmu)
pmu->pmu_enable(pmu);
}
static DEFINE_PER_CPU(struct list_head, rotation_list);
/*
* perf_pmu_rotate_start() and perf_rotate_context() are fully serialized
* because they're strictly cpu affine and rotate_start is called with IRQs
* disabled, while rotate_context is called from IRQ context.
*/
static void perf_pmu_rotate_start(struct pmu *pmu)
{
struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
struct list_head *head = &__get_cpu_var(rotation_list);
if (hrtimer_active(&cpuctx->timer))
return;
WARN_ON(!irqs_disabled());
__hrtimer_start_range_ns(&cpuctx->timer,
ns_to_ktime(cpuctx->timer_interval), 0,
HRTIMER_MODE_REL_PINNED, 0);
}
static void perf_pmu_rotate_stop(struct pmu *pmu)
{
struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
hrtimer_cancel(&cpuctx->timer);
if (list_empty(&cpuctx->rotation_list))
list_add(&cpuctx->rotation_list, head);
}
static void get_ctx(struct perf_event_context *ctx)
@ -1607,36 +1606,33 @@ static void rotate_ctx(struct perf_event_context *ctx)
}
/*
* Cannot race with ->pmu_rotate_start() because this is ran from hardirq
* context, and ->pmu_rotate_start() is called with irqs disabled (both are
* cpu affine, so there are no SMP races).
* perf_pmu_rotate_start() and perf_rotate_context() are fully serialized
* because they're strictly cpu affine and rotate_start is called with IRQs
* disabled, while rotate_context is called from IRQ context.
*/
static enum hrtimer_restart perf_event_context_tick(struct hrtimer *timer)
static void perf_rotate_context(struct perf_cpu_context *cpuctx)
{
enum hrtimer_restart restart = HRTIMER_NORESTART;
struct perf_cpu_context *cpuctx;
u64 interval = (u64)cpuctx->jiffies_interval * TICK_NSEC;
struct perf_event_context *ctx = NULL;
int rotate = 0;
cpuctx = container_of(timer, struct perf_cpu_context, timer);
int rotate = 0, remove = 1;
if (cpuctx->ctx.nr_events) {
restart = HRTIMER_RESTART;
remove = 0;
if (cpuctx->ctx.nr_events != cpuctx->ctx.nr_active)
rotate = 1;
}
ctx = cpuctx->task_ctx;
if (ctx && ctx->nr_events) {
restart = HRTIMER_RESTART;
remove = 0;
if (ctx->nr_events != ctx->nr_active)
rotate = 1;
}
perf_pmu_disable(cpuctx->ctx.pmu);
perf_ctx_adjust_freq(&cpuctx->ctx, cpuctx->timer_interval);
perf_ctx_adjust_freq(&cpuctx->ctx, interval);
if (ctx)
perf_ctx_adjust_freq(ctx, cpuctx->timer_interval);
perf_ctx_adjust_freq(ctx, interval);
if (!rotate)
goto done;
@ -1654,10 +1650,24 @@ static enum hrtimer_restart perf_event_context_tick(struct hrtimer *timer)
task_ctx_sched_in(ctx, EVENT_FLEXIBLE);
done:
perf_pmu_enable(cpuctx->ctx.pmu);
hrtimer_forward_now(timer, ns_to_ktime(cpuctx->timer_interval));
if (remove)
list_del_init(&cpuctx->rotation_list);
return restart;
perf_pmu_enable(cpuctx->ctx.pmu);
}
void perf_event_task_tick(void)
{
struct list_head *head = &__get_cpu_var(rotation_list);
struct perf_cpu_context *cpuctx, *tmp;
WARN_ON(!irqs_disabled());
list_for_each_entry_safe(cpuctx, tmp, head, rotation_list) {
if (cpuctx->jiffies_interval == 1 ||
!(jiffies % cpuctx->jiffies_interval))
perf_rotate_context(cpuctx);
}
}
static int event_enable_on_exec(struct perf_event *event,
@ -5186,9 +5196,8 @@ int perf_pmu_register(struct pmu *pmu)
__perf_event_init_context(&cpuctx->ctx);
cpuctx->ctx.type = cpu_context;
cpuctx->ctx.pmu = pmu;
cpuctx->timer_interval = TICK_NSEC;
hrtimer_init(&cpuctx->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
cpuctx->timer.function = perf_event_context_tick;
cpuctx->jiffies_interval = 1;
INIT_LIST_HEAD(&cpuctx->rotation_list);
}
got_cpu_context:
@ -6229,6 +6238,7 @@ static void __init perf_event_init_all_cpus(void)
for_each_possible_cpu(cpu) {
swhash = &per_cpu(swevent_htable, cpu);
mutex_init(&swhash->hlist_mutex);
INIT_LIST_HEAD(&per_cpu(rotation_list, cpu));
}
}
@ -6248,6 +6258,15 @@ static void __cpuinit perf_event_init_cpu(int cpu)
}
#ifdef CONFIG_HOTPLUG_CPU
static void perf_pmu_rotate_stop(struct pmu *pmu)
{
struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
WARN_ON(!irqs_disabled());
list_del_init(&cpuctx->rotation_list);
}
static void __perf_event_exit_context(void *__info)
{
struct perf_event_context *ctx = __info;

2
kernel/sched.c
View File

@ -3584,6 +3584,8 @@ void scheduler_tick(void)
curr->sched_class->task_tick(rq, curr, 0);
raw_spin_unlock(&rq->lock);
perf_event_task_tick();
#ifdef CONFIG_SMP
rq->idle_at_tick = idle_cpu(cpu);
trigger_load_balance(rq, cpu);