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perf counters: hw driver API
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Impact: restructure code, introduce hw_ops driver abstraction

Introduce this abstraction to handle counter details:

 struct hw_perf_counter_ops {
	void (*hw_perf_counter_enable)	(struct perf_counter *counter);
	void (*hw_perf_counter_disable)	(struct perf_counter *counter);
	void (*hw_perf_counter_read)	(struct perf_counter *counter);
 };

This will be useful to support assymetric hw details, and it will also
be useful to implement "software counters". (Counters that count kernel
managed sw events such as pagefaults, context-switches, wall-clock time
or task-local time.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Ingo Molnar committed Dec 11, 2008
1 parent ccff286 commit 621a01e
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Showing 3 changed files with 66 additions and 31 deletions.
37 changes: 27 additions & 10 deletions arch/x86/kernel/cpu/perf_counter.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -56,7 +56,7 @@ const int max_intel_perfmon_events = ARRAY_SIZE(intel_perfmon_event_map);
/*
* Setup the hardware configuration for a given hw_event_type
*/
int hw_perf_counter_init(struct perf_counter *counter)
static int __hw_perf_counter_init(struct perf_counter *counter)
{
struct perf_counter_hw_event *hw_event = &counter->hw_event;
struct hw_perf_counter *hwc = &counter->hw;
Expand Down Expand Up @@ -135,7 +135,7 @@ u64 hw_perf_disable_all(void)
EXPORT_SYMBOL_GPL(hw_perf_disable_all);

static inline void
__hw_perf_counter_disable(struct hw_perf_counter *hwc, unsigned int idx)
__x86_perf_counter_disable(struct hw_perf_counter *hwc, unsigned int idx)
{
wrmsr(hwc->config_base + idx, hwc->config, 0);
}
Expand All @@ -149,13 +149,13 @@ static void __hw_perf_counter_set_period(struct hw_perf_counter *hwc, int idx)
wrmsr(hwc->counter_base + idx, hwc->next_count, 0);
}

static void __hw_perf_counter_enable(struct hw_perf_counter *hwc, int idx)
static void __x86_perf_counter_enable(struct hw_perf_counter *hwc, int idx)
{
wrmsr(hwc->config_base + idx,
hwc->config | ARCH_PERFMON_EVENTSEL0_ENABLE, 0);
}

void hw_perf_counter_enable(struct perf_counter *counter)
static void x86_perf_counter_enable(struct perf_counter *counter)
{
struct cpu_hw_counters *cpuc = &__get_cpu_var(cpu_hw_counters);
struct hw_perf_counter *hwc = &counter->hw;
Expand All @@ -170,12 +170,12 @@ void hw_perf_counter_enable(struct perf_counter *counter)

perf_counters_lapic_init(hwc->nmi);

__hw_perf_counter_disable(hwc, idx);
__x86_perf_counter_disable(hwc, idx);

cpuc->counters[idx] = counter;

__hw_perf_counter_set_period(hwc, idx);
__hw_perf_counter_enable(hwc, idx);
__x86_perf_counter_enable(hwc, idx);
}

#ifdef CONFIG_X86_64
Expand Down Expand Up @@ -282,20 +282,20 @@ void perf_counter_print_debug(void)
local_irq_enable();
}

void hw_perf_counter_disable(struct perf_counter *counter)
static void x86_perf_counter_disable(struct perf_counter *counter)
{
struct cpu_hw_counters *cpuc = &__get_cpu_var(cpu_hw_counters);
struct hw_perf_counter *hwc = &counter->hw;
unsigned int idx = hwc->idx;

__hw_perf_counter_disable(hwc, idx);
__x86_perf_counter_disable(hwc, idx);

clear_bit(idx, cpuc->used);
cpuc->counters[idx] = NULL;
__hw_perf_save_counter(counter, hwc, idx);
}

void hw_perf_counter_read(struct perf_counter *counter)
static void x86_perf_counter_read(struct perf_counter *counter)
{
struct hw_perf_counter *hwc = &counter->hw;
unsigned long addr = hwc->counter_base + hwc->idx;
Expand Down Expand Up @@ -342,7 +342,7 @@ static void perf_save_and_restart(struct perf_counter *counter)
__hw_perf_counter_set_period(hwc, idx);

if (pmc_ctrl & ARCH_PERFMON_EVENTSEL0_ENABLE)
__hw_perf_counter_enable(hwc, idx);
__x86_perf_counter_enable(hwc, idx);
}

static void
Expand Down Expand Up @@ -572,3 +572,20 @@ void __init init_hw_perf_counters(void)

perf_counters_initialized = true;
}

static struct hw_perf_counter_ops x86_perf_counter_ops = {
.hw_perf_counter_enable = x86_perf_counter_enable,
.hw_perf_counter_disable = x86_perf_counter_disable,
.hw_perf_counter_read = x86_perf_counter_read,
};

struct hw_perf_counter_ops *hw_perf_counter_init(struct perf_counter *counter)
{
int err;

err = __hw_perf_counter_init(counter);
if (err)
return NULL;

return &x86_perf_counter_ops;
}
15 changes: 15 additions & 0 deletions include/linux/perf_counter.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -113,13 +113,25 @@ struct perf_data {
u8 data[PERF_DATA_BUFLEN];
};

struct perf_counter;

/**
* struct hw_perf_counter_ops - performance counter hw ops
*/
struct hw_perf_counter_ops {
void (*hw_perf_counter_enable) (struct perf_counter *counter);
void (*hw_perf_counter_disable) (struct perf_counter *counter);
void (*hw_perf_counter_read) (struct perf_counter *counter);
};

/**
* struct perf_counter - performance counter kernel representation:
*/
struct perf_counter {
struct list_head list_entry;
struct list_head sibling_list;
struct perf_counter *group_leader;
struct hw_perf_counter_ops *hw_ops;

int active;
#if BITS_PER_LONG == 64
Expand Down Expand Up @@ -185,6 +197,9 @@ struct perf_cpu_context {
extern int perf_max_counters;

#ifdef CONFIG_PERF_COUNTERS
extern struct hw_perf_counter_ops *
hw_perf_counter_init(struct perf_counter *counter);

extern void perf_counter_task_sched_in(struct task_struct *task, int cpu);
extern void perf_counter_task_sched_out(struct task_struct *task, int cpu);
extern void perf_counter_task_tick(struct task_struct *task, int cpu);
Expand Down
45 changes: 24 additions & 21 deletions kernel/perf_counter.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -37,18 +37,15 @@ static DEFINE_MUTEX(perf_resource_mutex);
/*
* Architecture provided APIs - weak aliases:
*/

int __weak hw_perf_counter_init(struct perf_counter *counter)
extern __weak struct hw_perf_counter_ops *
hw_perf_counter_init(struct perf_counter *counter)
{
return -EINVAL;
return ERR_PTR(-EINVAL);
}

void __weak hw_perf_counter_enable(struct perf_counter *counter) { }
void __weak hw_perf_counter_disable(struct perf_counter *counter) { }
void __weak hw_perf_counter_read(struct perf_counter *counter) { }
void __weak hw_perf_disable_all(void) { }
void __weak hw_perf_enable_all(void) { }
void __weak hw_perf_counter_setup(void) { }
void __weak hw_perf_disable_all(void) { }
void __weak hw_perf_enable_all(void) { }
void __weak hw_perf_counter_setup(void) { }

#if BITS_PER_LONG == 64

Expand Down Expand Up @@ -146,7 +143,7 @@ static void __perf_counter_remove_from_context(void *info)
spin_lock(&ctx->lock);

if (counter->active) {
hw_perf_counter_disable(counter);
counter->hw_ops->hw_perf_counter_disable(counter);
counter->active = 0;
ctx->nr_active--;
cpuctx->active_oncpu--;
Expand Down Expand Up @@ -257,7 +254,7 @@ static void __perf_install_in_context(void *info)
ctx->nr_counters++;

if (cpuctx->active_oncpu < perf_max_counters) {
hw_perf_counter_enable(counter);
counter->hw_ops->hw_perf_counter_enable(counter);
counter->active = 1;
counter->oncpu = cpu;
ctx->nr_active++;
Expand Down Expand Up @@ -333,7 +330,7 @@ counter_sched_out(struct perf_counter *counter,
if (!counter->active)
return;

hw_perf_counter_disable(counter);
counter->hw_ops->hw_perf_counter_disable(counter);
counter->active = 0;
counter->oncpu = -1;

Expand Down Expand Up @@ -392,7 +389,7 @@ counter_sched_in(struct perf_counter *counter,
struct perf_counter_context *ctx,
int cpu)
{
hw_perf_counter_enable(counter);
counter->hw_ops->hw_perf_counter_enable(counter);
counter->active = 1;
counter->oncpu = cpu; /* TODO: put 'cpu' into cpuctx->cpu */

Expand Down Expand Up @@ -509,7 +506,9 @@ void perf_counter_init_task(struct task_struct *task)
*/
static void __hw_perf_counter_read(void *info)
{
hw_perf_counter_read(info);
struct perf_counter *counter = info;

counter->hw_ops->hw_perf_counter_read(counter);
}

static u64 perf_counter_read(struct perf_counter *counter)
Expand Down Expand Up @@ -816,8 +815,10 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
int cpu,
struct perf_counter *group_leader)
{
struct perf_counter *counter = kzalloc(sizeof(*counter), GFP_KERNEL);
struct hw_perf_counter_ops *hw_ops;
struct perf_counter *counter;

counter = kzalloc(sizeof(*counter), GFP_KERNEL);
if (!counter)
return NULL;

Expand All @@ -839,6 +840,14 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
counter->hw_event = *hw_event;
counter->wakeup_pending = 0;
counter->group_leader = group_leader;
counter->hw_ops = NULL;

hw_ops = hw_perf_counter_init(counter);
if (!hw_ops) {
kfree(counter);
return NULL;
}
counter->hw_ops = hw_ops;

return counter;
}
Expand Down Expand Up @@ -908,10 +917,6 @@ asmlinkage int sys_perf_counter_open(
if (!counter)
goto err_put_context;

ret = hw_perf_counter_init(counter);
if (ret)
goto err_free_put_context;

perf_install_in_context(ctx, counter, cpu);

ret = anon_inode_getfd("[perf_counter]", &perf_fops, counter, 0);
Expand All @@ -927,8 +932,6 @@ asmlinkage int sys_perf_counter_open(
mutex_lock(&counter->mutex);
perf_counter_remove_from_context(counter);
mutex_unlock(&counter->mutex);

err_free_put_context:
kfree(counter);

err_put_context:
Expand Down

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