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Commit b9cacc7b authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: more elaborate write API 



Provide a begin, copy, end interface to the output buffer.

begin() reserves the space,
 copy() copies the data over, considering page boundaries,
  end() finalizes the event and does the wakeup.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Orig-LKML-Reference: <20090325113316.740550870@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c7138f37

kernel/perf_counter.c

+75 −34
Original line number Original line Diff line number Diff line
@@ -9,6 +9,7 @@ 
 */

 */





#include <linux/fs.h>

#include <linux/fs.h>

#include <linux/mm.h>

#include <linux/cpu.h>

#include <linux/cpu.h>

#include <linux/smp.h>

#include <linux/smp.h>

#include <linux/file.h>

#include <linux/file.h>
@@ -16,15 +17,14 @@ 
#include <linux/sysfs.h>

#include <linux/sysfs.h>

#include <linux/ptrace.h>

#include <linux/ptrace.h>

#include <linux/percpu.h>

#include <linux/percpu.h>

#include <linux/vmstat.h>

#include <linux/hardirq.h>

#include <linux/rculist.h>

#include <linux/uaccess.h>

#include <linux/uaccess.h>

#include <linux/syscalls.h>

#include <linux/syscalls.h>

#include <linux/anon_inodes.h>

#include <linux/anon_inodes.h>

#include <linux/kernel_stat.h>

#include <linux/kernel_stat.h>

#include <linux/perf_counter.h>

#include <linux/perf_counter.h>

#include <linux/mm.h>

#include <linux/vmstat.h>

#include <linux/rculist.h>

#include <linux/hardirq.h>





#include <asm/irq_regs.h>

#include <asm/irq_regs.h>
@@ -1411,16 +1411,20 @@ static const struct file_operations perf_fops = { 
 * Output

 * Output

 */

 */





static int perf_output_write(struct perf_counter *counter, int nmi,

struct perf_output_handle {

			     void *buf, ssize_t size)

	struct perf_counter	*counter;

	struct perf_mmap_data	*data;

	unsigned int		offset;

	int			wakeup;

};



static int perf_output_begin(struct perf_output_handle *handle,

			     struct perf_counter *counter, unsigned int size)

{

{

	struct perf_mmap_data *data;

	struct perf_mmap_data *data;

	unsigned int offset, head, nr;

	unsigned int offset, head;

	unsigned int len;

	int ret, wakeup;





	rcu_read_lock();

	rcu_read_lock();

	ret = -ENOSPC;

	data = rcu_dereference(counter->data);

	data = rcu_dereference(counter->data);

	if (!data)

	if (!data)

		goto out;

		goto out;
@@ -1428,45 +1432,82 @@ static int perf_output_write(struct perf_counter *counter, int nmi, 
	if (!data->nr_pages)

	if (!data->nr_pages)

		goto out;

		goto out;





	ret = -EINVAL;

	if (size > PAGE_SIZE)

		goto out;



	do {

	do {

		offset = head = atomic_read(&data->head);

		offset = head = atomic_read(&data->head);

		head += size;

		head += size;

	} while (atomic_cmpxchg(&data->head, offset, head) != offset);

	} while (atomic_cmpxchg(&data->head, offset, head) != offset);





	wakeup = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT);

	handle->counter	= counter;

	handle->data	= data;

	handle->offset	= offset;

	handle->wakeup	= (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT);





	nr = (offset >> PAGE_SHIFT) & (data->nr_pages - 1);

	return 0;

	offset &= PAGE_SIZE - 1;





	len = min_t(unsigned int, PAGE_SIZE - offset, size);

out:

	memcpy(data->data_pages[nr] + offset, buf, len);

	rcu_read_unlock();

	size -= len;





	if (size) {

	return -ENOSPC;

		nr = (nr + 1) & (data->nr_pages - 1);

		memcpy(data->data_pages[nr], buf + len, size);

}

}





	/*

static void perf_output_copy(struct perf_output_handle *handle,

	 * generate a poll() wakeup for every page boundary crossed

			     void *buf, unsigned int len)

	 */

{

	if (wakeup) {

	unsigned int pages_mask;

		atomic_xchg(&data->wakeup, POLL_IN);

	unsigned int offset;

		__perf_counter_update_userpage(counter, data);

	unsigned int size;

	void **pages;



	offset		= handle->offset;

	pages_mask	= handle->data->nr_pages - 1;

	pages		= handle->data->data_pages;



	do {

		unsigned int page_offset;

		int nr;



		nr	    = (offset >> PAGE_SHIFT) & pages_mask;

		page_offset = offset & (PAGE_SIZE - 1);

		size	    = min_t(unsigned int, PAGE_SIZE - page_offset, len);



		memcpy(pages[nr] + page_offset, buf, size);



		len	    -= size;

		buf	    += size;

		offset	    += size;

	} while (len);



	handle->offset = offset;

}



static void perf_output_end(struct perf_output_handle *handle, int nmi)

{

	if (handle->wakeup) {

		(void)atomic_xchg(&handle->data->wakeup, POLL_IN);

		__perf_counter_update_userpage(handle->counter, handle->data);

		if (nmi) {

		if (nmi) {

			counter->wakeup_pending = 1;

			handle->counter->wakeup_pending = 1;

			set_perf_counter_pending();

			set_perf_counter_pending();

		} else

		} else

			wake_up(&counter->waitq);

			wake_up(&handle->counter->waitq);

	}

	}

	ret = 0;

out:

	rcu_read_unlock();

	rcu_read_unlock();

}



static int perf_output_write(struct perf_counter *counter, int nmi,

			     void *buf, ssize_t size)

{

	struct perf_output_handle handle;

	int ret;





	ret = perf_output_begin(&handle, counter, size);

	if (ret)

		goto out;



	perf_output_copy(&handle, buf, size);

	perf_output_end(&handle, nmi);



out:

	return ret;

	return ret;

}

}