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perf_counter: new output ABI - part 1

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Impact: Rework the perfcounter output ABI

use sys_read() only for instant data and provide mmap() output for all
async overflow data.

The first mmap() determines the size of the output buffer. The mmap()
size must be a PAGE_SIZE multiple of 1+pages, where pages must be a
power of 2 or 0. Further mmap()s of the same fd must have the same
size. Once all maps are gone, you can again mmap() with a new size.

In case of 0 extra pages there is no data output and the first page
only contains meta data.

When there are data pages, a poll() event will be generated for each
full page of data. Furthermore, the output is circular. This means
that although 1 page is a valid configuration, its useless, since
we'll start overwriting it the instant we report a full page.

Future work will focus on the output format (currently maintained)
where we'll likey want each entry denoted by a header which includes a
type and length.

Further future work will allow to splice() the fd, also containing the
async overflow data -- splice() would be mutually exclusive with
mmap() of the data.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090323172417.470536358@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-03-23 18:22:10 +01:00 committed by Ingo Molnar
parent b09d2501ed
commit 7b732a7504
3 changed files with 263 additions and 246 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
arch/powerpc/kernel/perf_counter.c
View file

@ -417,7 +417,6 @@ void hw_perf_restore(u64 disable)
atomic64_set(&counter->hw.prev_count, val);
counter->hw.idx = hwc_index[i] + 1;
write_pmc(counter->hw.idx, val);
if (counter->user_page)
perf_counter_update_userpage(counter);
}
mb();
@ -574,7 +573,6 @@ static void power_perf_disable(struct perf_counter *counter)
ppmu->disable_pmc(counter->hw.idx - 1, cpuhw->mmcr);
write_pmc(counter->hw.idx, 0);
counter->hw.idx = 0;
if (counter->user_page)
perf_counter_update_userpage(counter);
break;
}
@ -702,7 +700,6 @@ static void record_and_restart(struct perf_counter *counter, long val,
write_pmc(counter->hw.idx, val);
atomic64_set(&counter->hw.prev_count, val);
atomic64_set(&counter->hw.period_left, left);
if (counter->user_page)
perf_counter_update_userpage(counter);
/*

36
include/linux/perf_counter.h
View file

@ -152,6 +152,8 @@ struct perf_counter_mmap_page {
__u32 lock; /* seqlock for synchronization */
__u32 index; /* hardware counter identifier */
__s64 offset; /* add to hardware counter value */
__u32 data_head; /* head in the data section */
};
#ifdef __KERNEL__
@ -218,21 +220,6 @@ struct hw_perf_counter {
#endif
};
/*
* Hardcoded buffer length limit for now, for IRQ-fed events:
*/
#define PERF_DATA_BUFLEN 2048
/**
* struct perf_data - performance counter IRQ data sampling ...
*/
struct perf_data {
int len;
int rd_idx;
int overrun;
u8 data[PERF_DATA_BUFLEN];
};
struct perf_counter;
/**
@ -256,6 +243,14 @@ enum perf_counter_active_state {
struct file;
struct perf_mmap_data {
struct rcu_head rcu_head;
int nr_pages;
atomic_t head;
struct perf_counter_mmap_page *user_page;
void *data_pages[0];
};
/**
* struct perf_counter - performance counter kernel representation:
*/
@ -289,16 +284,15 @@ struct perf_counter {
int oncpu;
int cpu;
/* pointer to page shared with userspace via mmap */
unsigned long user_page;
/* mmap bits */
struct mutex mmap_mutex;
atomic_t mmap_count;
struct perf_mmap_data *data;
/* read() / irq related data */
/* poll related */
wait_queue_head_t waitq;
/* optional: for NMIs */
int wakeup_pending;
struct perf_data *irqdata;
struct perf_data *usrdata;
struct perf_data data[2];
void (*destroy)(struct perf_counter *);
struct rcu_head rcu_head;

464
kernel/perf_counter.c
View file

@ -4,7 +4,8 @@
* Copyright(C) 2008 Thomas Gleixner <tglx@linutronix.de>
* Copyright(C) 2008 Red Hat, Inc., Ingo Molnar
*
* For licencing details see kernel-base/COPYING
*
* For licensing details see kernel-base/COPYING
*/
#include <linux/fs.h>
@ -1022,66 +1023,6 @@ static u64 perf_counter_read(struct perf_counter *counter)
return atomic64_read(&counter->count);
}
/*
* Cross CPU call to switch performance data pointers
*/
static void __perf_switch_irq_data(void *info)
{
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_counter *counter = info;
struct perf_counter_context *ctx = counter->ctx;
struct perf_data *oldirqdata = counter->irqdata;
/*
* If this is a task context, we need to check whether it is
* the current task context of this cpu. If not it has been
* scheduled out before the smp call arrived.
*/
if (ctx->task) {
if (cpuctx->task_ctx != ctx)
return;
spin_lock(&ctx->lock);
}
/* Change the pointer NMI safe */
atomic_long_set((atomic_long_t *)&counter->irqdata,
(unsigned long) counter->usrdata);
counter->usrdata = oldirqdata;
if (ctx->task)
spin_unlock(&ctx->lock);
}
static struct perf_data *perf_switch_irq_data(struct perf_counter *counter)
{
struct perf_counter_context *ctx = counter->ctx;
struct perf_data *oldirqdata = counter->irqdata;
struct task_struct *task = ctx->task;
if (!task) {
smp_call_function_single(counter->cpu,
__perf_switch_irq_data,
counter, 1);
return counter->usrdata;
}
retry:
spin_lock_irq(&ctx->lock);
if (counter->state != PERF_COUNTER_STATE_ACTIVE) {
counter->irqdata = counter->usrdata;
counter->usrdata = oldirqdata;
spin_unlock_irq(&ctx->lock);
return oldirqdata;
}
spin_unlock_irq(&ctx->lock);
task_oncpu_function_call(task, __perf_switch_irq_data, counter);
/* Might have failed, because task was scheduled out */
if (counter->irqdata == oldirqdata)
goto retry;
return counter->usrdata;
}
static void put_context(struct perf_counter_context *ctx)
{
if (ctx->task)
@ -1177,7 +1118,6 @@ static int perf_release(struct inode *inode, struct file *file)
mutex_unlock(&counter->mutex);
mutex_unlock(&ctx->mutex);
free_page(counter->user_page);
free_counter(counter);
put_context(ctx);
@ -1192,7 +1132,7 @@ perf_read_hw(struct perf_counter *counter, char __user *buf, size_t count)
{
u64 cntval;
if (count != sizeof(cntval))
if (count < sizeof(cntval))
return -EINVAL;
/*
@ -1210,122 +1150,21 @@ perf_read_hw(struct perf_counter *counter, char __user *buf, size_t count)
return put_user(cntval, (u64 __user *) buf) ? -EFAULT : sizeof(cntval);
}
static ssize_t
perf_copy_usrdata(struct perf_data *usrdata, char __user *buf, size_t count)
{
if (!usrdata->len)
return 0;
count = min(count, (size_t)usrdata->len);
if (copy_to_user(buf, usrdata->data + usrdata->rd_idx, count))
return -EFAULT;
/* Adjust the counters */
usrdata->len -= count;
if (!usrdata->len)
usrdata->rd_idx = 0;
else
usrdata->rd_idx += count;
return count;
}
static ssize_t
perf_read_irq_data(struct perf_counter *counter,
char __user *buf,
size_t count,
int nonblocking)
{
struct perf_data *irqdata, *usrdata;
DECLARE_WAITQUEUE(wait, current);
ssize_t res, res2;
irqdata = counter->irqdata;
usrdata = counter->usrdata;
if (usrdata->len + irqdata->len >= count)
goto read_pending;
if (nonblocking)
return -EAGAIN;
spin_lock_irq(&counter->waitq.lock);
__add_wait_queue(&counter->waitq, &wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
if (usrdata->len + irqdata->len >= count)
break;
if (signal_pending(current))
break;
if (counter->state == PERF_COUNTER_STATE_ERROR)
break;
spin_unlock_irq(&counter->waitq.lock);
schedule();
spin_lock_irq(&counter->waitq.lock);
}
__remove_wait_queue(&counter->waitq, &wait);
__set_current_state(TASK_RUNNING);
spin_unlock_irq(&counter->waitq.lock);
if (usrdata->len + irqdata->len < count &&
counter->state != PERF_COUNTER_STATE_ERROR)
return -ERESTARTSYS;
read_pending:
mutex_lock(&counter->mutex);
/* Drain pending data first: */
res = perf_copy_usrdata(usrdata, buf, count);
if (res < 0 || res == count)
goto out;
/* Switch irq buffer: */
usrdata = perf_switch_irq_data(counter);
res2 = perf_copy_usrdata(usrdata, buf + res, count - res);
if (res2 < 0) {
if (!res)
res = -EFAULT;
} else {
res += res2;
}
out:
mutex_unlock(&counter->mutex);
return res;
}
static ssize_t
perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
struct perf_counter *counter = file->private_data;
switch (counter->hw_event.record_type) {
case PERF_RECORD_SIMPLE:
return perf_read_hw(counter, buf, count);
case PERF_RECORD_IRQ:
case PERF_RECORD_GROUP:
return perf_read_irq_data(counter, buf, count,
file->f_flags & O_NONBLOCK);
}
return -EINVAL;
}
static unsigned int perf_poll(struct file *file, poll_table *wait)
{
struct perf_counter *counter = file->private_data;
unsigned int events = 0;
unsigned long flags;
unsigned int events = POLLIN;
poll_wait(file, &counter->waitq, wait);
spin_lock_irqsave(&counter->waitq.lock, flags);
if (counter->usrdata->len || counter->irqdata->len)
events |= POLLIN;
spin_unlock_irqrestore(&counter->waitq.lock, flags);
return events;
}
@ -1347,78 +1186,207 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
return err;
}
void perf_counter_update_userpage(struct perf_counter *counter)
static void __perf_counter_update_userpage(struct perf_counter *counter,
struct perf_mmap_data *data)
{
struct perf_counter_mmap_page *userpg;
if (!counter->user_page)
return;
userpg = (struct perf_counter_mmap_page *) counter->user_page;
struct perf_counter_mmap_page *userpg = data->user_page;
/*
* Disable preemption so as to not let the corresponding user-space
* spin too long if we get preempted.
*/
preempt_disable();
++userpg->lock;
smp_wmb();
userpg->index = counter->hw.idx;
userpg->offset = atomic64_read(&counter->count);
if (counter->state == PERF_COUNTER_STATE_ACTIVE)
userpg->offset -= atomic64_read(&counter->hw.prev_count);
userpg->data_head = atomic_read(&data->head);
smp_wmb();
++userpg->lock;
preempt_enable();
}
void perf_counter_update_userpage(struct perf_counter *counter)
{
struct perf_mmap_data *data;
rcu_read_lock();
data = rcu_dereference(counter->data);
if (data)
__perf_counter_update_userpage(counter, data);
rcu_read_unlock();
}
static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct perf_counter *counter = vma->vm_file->private_data;
struct perf_mmap_data *data;
int ret = VM_FAULT_SIGBUS;
if (!counter->user_page)
return VM_FAULT_SIGBUS;
rcu_read_lock();
data = rcu_dereference(counter->data);
if (!data)
goto unlock;
vmf->page = virt_to_page(counter->user_page);
if (vmf->pgoff == 0) {
vmf->page = virt_to_page(data->user_page);
} else {
int nr = vmf->pgoff - 1;
if ((unsigned)nr > data->nr_pages)
goto unlock;
vmf->page = virt_to_page(data->data_pages[nr]);
}
get_page(vmf->page);
ret = 0;
unlock:
rcu_read_unlock();
return ret;
}
static int perf_mmap_data_alloc(struct perf_counter *counter, int nr_pages)
{
struct perf_mmap_data *data;
unsigned long size;
int i;
WARN_ON(atomic_read(&counter->mmap_count));
size = sizeof(struct perf_mmap_data);
size += nr_pages * sizeof(void *);
data = kzalloc(size, GFP_KERNEL);
if (!data)
goto fail;
data->user_page = (void *)get_zeroed_page(GFP_KERNEL);
if (!data->user_page)
goto fail_user_page;
for (i = 0; i < nr_pages; i++) {
data->data_pages[i] = (void *)get_zeroed_page(GFP_KERNEL);
if (!data->data_pages[i])
goto fail_data_pages;
}
data->nr_pages = nr_pages;
rcu_assign_pointer(counter->data, data);
return 0;
fail_data_pages:
for (i--; i >= 0; i--)
free_page((unsigned long)data->data_pages[i]);
free_page((unsigned long)data->user_page);
fail_user_page:
kfree(data);
fail:
return -ENOMEM;
}
static void __perf_mmap_data_free(struct rcu_head *rcu_head)
{
struct perf_mmap_data *data = container_of(rcu_head,
struct perf_mmap_data, rcu_head);
int i;
free_page((unsigned long)data->user_page);
for (i = 0; i < data->nr_pages; i++)
free_page((unsigned long)data->data_pages[i]);
kfree(data);
}
static void perf_mmap_data_free(struct perf_counter *counter)
{
struct perf_mmap_data *data = counter->data;
WARN_ON(atomic_read(&counter->mmap_count));
rcu_assign_pointer(counter->data, NULL);
call_rcu(&data->rcu_head, __perf_mmap_data_free);
}
static void perf_mmap_open(struct vm_area_struct *vma)
{
struct perf_counter *counter = vma->vm_file->private_data;
atomic_inc(&counter->mmap_count);
}
static void perf_mmap_close(struct vm_area_struct *vma)
{
struct perf_counter *counter = vma->vm_file->private_data;
if (atomic_dec_and_mutex_lock(&counter->mmap_count,
&counter->mmap_mutex)) {
perf_mmap_data_free(counter);
mutex_unlock(&counter->mmap_mutex);
}
}
static struct vm_operations_struct perf_mmap_vmops = {
.open = perf_mmap_open,
.close = perf_mmap_close,
.fault = perf_mmap_fault,
};
static int perf_mmap(struct file *file, struct vm_area_struct *vma)
{
struct perf_counter *counter = file->private_data;
unsigned long userpg;
unsigned long vma_size;
unsigned long nr_pages;
unsigned long locked, lock_limit;
int ret = 0;
if (!(vma->vm_flags & VM_SHARED) || (vma->vm_flags & VM_WRITE))
return -EINVAL;
if (vma->vm_end - vma->vm_start != PAGE_SIZE)
vma_size = vma->vm_end - vma->vm_start;
nr_pages = (vma_size / PAGE_SIZE) - 1;
if (nr_pages == 0 || !is_power_of_2(nr_pages))
return -EINVAL;
/*
* For now, restrict to the case of a hardware counter
* on the current task.
*/
if (is_software_counter(counter) || counter->task != current)
if (vma_size != PAGE_SIZE * (1 + nr_pages))
return -EINVAL;
userpg = counter->user_page;
if (!userpg) {
userpg = get_zeroed_page(GFP_KERNEL);
mutex_lock(&counter->mutex);
if (counter->user_page) {
free_page(userpg);
userpg = counter->user_page;
} else {
counter->user_page = userpg;
}
mutex_unlock(&counter->mutex);
if (!userpg)
return -ENOMEM;
}
if (vma->vm_pgoff != 0)
return -EINVAL;
perf_counter_update_userpage(counter);
locked = vma_size >> PAGE_SHIFT;
locked += vma->vm_mm->locked_vm;
lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
lock_limit >>= PAGE_SHIFT;
if ((locked > lock_limit) && !capable(CAP_IPC_LOCK))
return -EPERM;
mutex_lock(&counter->mmap_mutex);
if (atomic_inc_not_zero(&counter->mmap_count))
goto out;
WARN_ON(counter->data);
ret = perf_mmap_data_alloc(counter, nr_pages);
if (!ret)
atomic_set(&counter->mmap_count, 1);
out:
mutex_unlock(&counter->mmap_mutex);
vma->vm_flags &= ~VM_MAYWRITE;
vma->vm_flags |= VM_RESERVED;
vma->vm_ops = &perf_mmap_vmops;
return 0;
return ret;
}
static const struct file_operations perf_fops = {
@ -1434,30 +1402,94 @@ static const struct file_operations perf_fops = {
* Output
*/
static void perf_counter_store_irq(struct perf_counter *counter, u64 data)
static int perf_output_write(struct perf_counter *counter, int nmi,
void *buf, ssize_t size)
{
struct perf_data *irqdata = counter->irqdata;
struct perf_mmap_data *data;
unsigned int offset, head, nr;
unsigned int len;
int ret, wakeup;
if (irqdata->len > PERF_DATA_BUFLEN - sizeof(u64)) {
irqdata->overrun++;
} else {
u64 *p = (u64 *) &irqdata->data[irqdata->len];
rcu_read_lock();
ret = -ENOSPC;
data = rcu_dereference(counter->data);
if (!data)
goto out;
*p = data;
irqdata->len += sizeof(u64);
}
if (!data->nr_pages)
goto out;
ret = -EINVAL;
if (size > PAGE_SIZE)
goto out;
do {
offset = head = atomic_read(&data->head);
head += sizeof(u64);
} while (atomic_cmpxchg(&data->head, offset, head) != offset);
wakeup = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT);
nr = (offset >> PAGE_SHIFT) & (data->nr_pages - 1);
offset &= PAGE_SIZE - 1;
len = min_t(unsigned int, PAGE_SIZE - offset, size);
memcpy(data->data_pages[nr] + offset, buf, len);
size -= len;
if (size) {
nr = (nr + 1) & (data->nr_pages - 1);
memcpy(data->data_pages[nr], buf + len, size);
}
static void perf_counter_handle_group(struct perf_counter *counter)
/*
* generate a poll() wakeup for every page boundary crossed
*/
if (wakeup) {
__perf_counter_update_userpage(counter, data);
if (nmi) {
counter->wakeup_pending = 1;
set_perf_counter_pending();
} else
wake_up(&counter->waitq);
}
ret = 0;
out:
rcu_read_unlock();
return ret;
}
static void perf_output_simple(struct perf_counter *counter,
int nmi, struct pt_regs *regs)
{
u64 entry;
entry = instruction_pointer(regs);
perf_output_write(counter, nmi, &entry, sizeof(entry));
}
struct group_entry {
u64 event;
u64 counter;
};
static void perf_output_group(struct perf_counter *counter, int nmi)
{
struct perf_counter *leader, *sub;
leader = counter->group_leader;
list_for_each_entry(sub, &leader->sibling_list, list_entry) {
struct group_entry entry;
if (sub != counter)
sub->hw_ops->read(sub);
perf_counter_store_irq(counter, sub->hw_event.config);
perf_counter_store_irq(counter, atomic64_read(&sub->count));
entry.event = sub->hw_event.config;
entry.counter = atomic64_read(&sub->count);
perf_output_write(counter, nmi, &entry, sizeof(entry));
}
}
@ -1469,19 +1501,13 @@ void perf_counter_output(struct perf_counter *counter,
return;
case PERF_RECORD_IRQ:
perf_counter_store_irq(counter, instruction_pointer(regs));
perf_output_simple(counter, nmi, regs);
break;
case PERF_RECORD_GROUP:
perf_counter_handle_group(counter);
perf_output_group(counter, nmi);
break;
}
if (nmi) {
counter->wakeup_pending = 1;
set_perf_counter_pending();
} else
wake_up(&counter->waitq);
}
/*
@ -1967,10 +1993,10 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
INIT_LIST_HEAD(&counter->sibling_list);
init_waitqueue_head(&counter->waitq);
mutex_init(&counter->mmap_mutex);
INIT_LIST_HEAD(&counter->child_list);
counter->irqdata = &counter->data[0];
counter->usrdata = &counter->data[1];
counter->cpu = cpu;
counter->hw_event = *hw_event;
counter->wakeup_pending = 0;