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Commit 906010b2 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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perf_event: Provide vmalloc() based mmap() backing 



Some architectures such as Sparc, ARM and MIPS (basically
everything with flush_dcache_page()) need to deal with dcache
aliases by carefully placing pages in both kernel and user maps.

These architectures typically have to use vmalloc_user() for this.

However, on other architectures, vmalloc() is not needed and has
the downsides of being more restricted and slower than regular
allocations.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarDavid Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1254830228.21044.272.camel@laptop>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e13dbd7d

arch/sparc/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ config SPARC 
	select RTC_CLASS

	select RTC_DRV_M48T59

	select HAVE_PERF_EVENTS

	select PERF_USE_VMALLOC

	select HAVE_DMA_ATTRS

	select HAVE_DMA_API_DEBUG
@@ -48,6 +49,7 @@ config SPARC64 
	select RTC_DRV_SUN4V

	select RTC_DRV_STARFIRE

	select HAVE_PERF_EVENTS

	select PERF_USE_VMALLOC



config ARCH_DEFCONFIG

	string

include/linux/perf_event.h

+5 −0
Original line number Diff line number Diff line
@@ -442,6 +442,7 @@ enum perf_callchain_context { 
#include <linux/hrtimer.h>

#include <linux/fs.h>

#include <linux/pid_namespace.h>

#include <linux/workqueue.h>

#include <asm/atomic.h>



#define PERF_MAX_STACK_DEPTH		255
@@ -513,6 +514,10 @@ struct file; 


struct perf_mmap_data {

	struct rcu_head			rcu_head;

#ifdef CONFIG_PERF_USE_VMALLOC

	struct work_struct		work;

#endif

	int				data_order;

	int				nr_pages;	/* nr of data pages  */

	int				writable;	/* are we writable   */

	int				nr_locked;	/* nr pages mlocked  */

init/Kconfig

+18 −0
Original line number Diff line number Diff line
@@ -921,6 +921,11 @@ config HAVE_PERF_EVENTS 
	help

	  See tools/perf/design.txt for details.



config PERF_USE_VMALLOC

	bool

	help

	  See tools/perf/design.txt for details



menu "Kernel Performance Events And Counters"



config PERF_EVENTS
@@ -976,6 +981,19 @@ config PERF_COUNTERS 


	  Say N if unsure.



config DEBUG_PERF_USE_VMALLOC

	default n

	bool "Debug: use vmalloc to back perf mmap() buffers"

	depends on PERF_EVENTS && DEBUG_KERNEL

	select PERF_USE_VMALLOC

	help

	 Use vmalloc memory to back perf mmap() buffers.



	 Mostly useful for debugging the vmalloc code on platforms

	 that don't require it.



	 Say N if unsure.



endmenu



config VM_EVENT_COUNTERS

kernel/perf_event.c

+186 −62
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <linux/percpu.h>

#include <linux/ptrace.h>

#include <linux/vmstat.h>

#include <linux/vmalloc.h>

#include <linux/hardirq.h>

#include <linux/rculist.h>

#include <linux/uaccess.h>
@@ -2091,49 +2092,31 @@ void perf_event_update_userpage(struct perf_event *event) 
	rcu_read_unlock();

}



static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)

static unsigned long perf_data_size(struct perf_mmap_data *data)

{

	struct perf_event *event = vma->vm_file->private_data;

	struct perf_mmap_data *data;

	int ret = VM_FAULT_SIGBUS;



	if (vmf->flags & FAULT_FLAG_MKWRITE) {

		if (vmf->pgoff == 0)

			ret = 0;

		return ret;

	return data->nr_pages << (PAGE_SHIFT + data->data_order);

}



	rcu_read_lock();

	data = rcu_dereference(event->data);

	if (!data)

		goto unlock;



	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;

#ifndef CONFIG_PERF_USE_VMALLOC



		if (vmf->flags & FAULT_FLAG_WRITE)

			goto unlock;



		vmf->page = virt_to_page(data->data_pages[nr]);

	}

/*

 * Back perf_mmap() with regular GFP_KERNEL-0 pages.

 */



	get_page(vmf->page);

	vmf->page->mapping = vma->vm_file->f_mapping;

	vmf->page->index   = vmf->pgoff;

static struct page *

perf_mmap_to_page(struct perf_mmap_data *data, unsigned long pgoff)

{

	if (pgoff > data->nr_pages)

		return NULL;



	ret = 0;

unlock:

	rcu_read_unlock();

	if (pgoff == 0)

		return virt_to_page(data->user_page);



	return ret;

	return virt_to_page(data->data_pages[pgoff - 1]);

}



static int perf_mmap_data_alloc(struct perf_event *event, int nr_pages)

static struct perf_mmap_data *

perf_mmap_data_alloc(struct perf_event *event, int nr_pages)

{

	struct perf_mmap_data *data;

	unsigned long size;
@@ -2158,19 +2141,10 @@ static int perf_mmap_data_alloc(struct perf_event *event, int nr_pages) 
			goto fail_data_pages;

	}



	data->data_order = 0;

	data->nr_pages = nr_pages;

	atomic_set(&data->lock, -1);



	if (event->attr.watermark) {

		data->watermark = min_t(long, PAGE_SIZE * nr_pages,

				      event->attr.wakeup_watermark);

	}

	if (!data->watermark)

		data->watermark = max(PAGE_SIZE, PAGE_SIZE * nr_pages / 4);



	rcu_assign_pointer(event->data, data);



	return 0;

	return data;



fail_data_pages:

	for (i--; i >= 0; i--)
@@ -2182,7 +2156,7 @@ static int perf_mmap_data_alloc(struct perf_event *event, int nr_pages) 
	kfree(data);



fail:

	return -ENOMEM;

	return NULL;

}



static void perf_mmap_free_page(unsigned long addr)
@@ -2193,28 +2167,169 @@ static void perf_mmap_free_page(unsigned long addr) 
	__free_page(page);

}



static void __perf_mmap_data_free(struct rcu_head *rcu_head)

static void perf_mmap_data_free(struct perf_mmap_data *data)

{

	struct perf_mmap_data *data;

	int i;



	data = container_of(rcu_head, struct perf_mmap_data, rcu_head);



	perf_mmap_free_page((unsigned long)data->user_page);

	for (i = 0; i < data->nr_pages; i++)

		perf_mmap_free_page((unsigned long)data->data_pages[i]);

}



#else



/*

 * Back perf_mmap() with vmalloc memory.

 *

 * Required for architectures that have d-cache aliasing issues.

 */



static struct page *

perf_mmap_to_page(struct perf_mmap_data *data, unsigned long pgoff)

{

	if (pgoff > (1UL << data->data_order))

		return NULL;



	return vmalloc_to_page((void *)data->user_page + pgoff * PAGE_SIZE);

}



static void perf_mmap_unmark_page(void *addr)

{

	struct page *page = vmalloc_to_page(addr);



	page->mapping = NULL;

}



static void perf_mmap_data_free_work(struct work_struct *work)

{

	struct perf_mmap_data *data;

	void *base;

	int i, nr;



	data = container_of(work, struct perf_mmap_data, work);

	nr = 1 << data->data_order;



	base = data->user_page;

	for (i = 0; i < nr + 1; i++)

		perf_mmap_unmark_page(base + (i * PAGE_SIZE));



	vfree(base);

}



static void perf_mmap_data_free(struct perf_mmap_data *data)

{

	schedule_work(&data->work);

}



static struct perf_mmap_data *

perf_mmap_data_alloc(struct perf_event *event, int nr_pages)

{

	struct perf_mmap_data *data;

	unsigned long size;

	void *all_buf;



	WARN_ON(atomic_read(&event->mmap_count));



	size = sizeof(struct perf_mmap_data);

	size += sizeof(void *);



	data = kzalloc(size, GFP_KERNEL);

	if (!data)

		goto fail;



	INIT_WORK(&data->work, perf_mmap_data_free_work);



	all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);

	if (!all_buf)

		goto fail_all_buf;



	data->user_page = all_buf;

	data->data_pages[0] = all_buf + PAGE_SIZE;

	data->data_order = ilog2(nr_pages);

	data->nr_pages = 1;



	return data;



fail_all_buf:

	kfree(data);



fail:

	return NULL;

}



#endif



static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)

{

	struct perf_event *event = vma->vm_file->private_data;

	struct perf_mmap_data *data;

	int ret = VM_FAULT_SIGBUS;



	if (vmf->flags & FAULT_FLAG_MKWRITE) {

		if (vmf->pgoff == 0)

			ret = 0;

		return ret;

	}



	rcu_read_lock();

	data = rcu_dereference(event->data);

	if (!data)

		goto unlock;



	if (vmf->pgoff && (vmf->flags & FAULT_FLAG_WRITE))

		goto unlock;



	vmf->page = perf_mmap_to_page(data, vmf->pgoff);

	if (!vmf->page)

		goto unlock;



	get_page(vmf->page);

	vmf->page->mapping = vma->vm_file->f_mapping;

	vmf->page->index   = vmf->pgoff;



	ret = 0;

unlock:

	rcu_read_unlock();



	return ret;

}



static void

perf_mmap_data_init(struct perf_event *event, struct perf_mmap_data *data)

{

	long max_size = perf_data_size(data);



	atomic_set(&data->lock, -1);



	if (event->attr.watermark) {

		data->watermark = min_t(long, max_size,

					event->attr.wakeup_watermark);

	}



	if (!data->watermark)

		data->watermark = max_t(long, PAGE_SIZE, max_size / 2);





	rcu_assign_pointer(event->data, data);

}



static void perf_mmap_data_free_rcu(struct rcu_head *rcu_head)

{

	struct perf_mmap_data *data;



	data = container_of(rcu_head, struct perf_mmap_data, rcu_head);

	perf_mmap_data_free(data);

	kfree(data);

}



static void perf_mmap_data_free(struct perf_event *event)

static void perf_mmap_data_release(struct perf_event *event)

{

	struct perf_mmap_data *data = event->data;



	WARN_ON(atomic_read(&event->mmap_count));



	rcu_assign_pointer(event->data, NULL);

	call_rcu(&data->rcu_head, __perf_mmap_data_free);

	call_rcu(&data->rcu_head, perf_mmap_data_free_rcu);

}



static void perf_mmap_open(struct vm_area_struct *vma)
@@ -2230,11 +2345,12 @@ static void perf_mmap_close(struct vm_area_struct *vma) 


	WARN_ON_ONCE(event->ctx->parent_ctx);

	if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) {

		unsigned long size = perf_data_size(event->data);

		struct user_struct *user = current_user();



		atomic_long_sub(event->data->nr_pages + 1, &user->locked_vm);

		atomic_long_sub((size >> PAGE_SHIFT) + 1, &user->locked_vm);

		vma->vm_mm->locked_vm -= event->data->nr_locked;

		perf_mmap_data_free(event);

		perf_mmap_data_release(event);

		mutex_unlock(&event->mmap_mutex);

	}

}
@@ -2252,6 +2368,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) 
	unsigned long user_locked, user_lock_limit;

	struct user_struct *user = current_user();

	unsigned long locked, lock_limit;

	struct perf_mmap_data *data;

	unsigned long vma_size;

	unsigned long nr_pages;

	long user_extra, extra;
@@ -2314,10 +2431,15 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) 
	}



	WARN_ON(event->data);

	ret = perf_mmap_data_alloc(event, nr_pages);

	if (ret)



	data = perf_mmap_data_alloc(event, nr_pages);

	ret = -ENOMEM;

	if (!data)

		goto unlock;



	ret = 0;

	perf_mmap_data_init(event, data);



	atomic_set(&event->mmap_count, 1);

	atomic_long_add(user_extra, &user->locked_vm);

	vma->vm_mm->locked_vm += extra;
@@ -2505,7 +2627,7 @@ static bool perf_output_space(struct perf_mmap_data *data, unsigned long tail, 
	if (!data->writable)

		return true;



	mask = (data->nr_pages << PAGE_SHIFT) - 1;

	mask = perf_data_size(data) - 1;



	offset = (offset - tail) & mask;

	head   = (head   - tail) & mask;
@@ -2610,7 +2732,7 @@ void perf_output_copy(struct perf_output_handle *handle, 
		      const void *buf, unsigned int len)

{

	unsigned int pages_mask;

	unsigned int offset;

	unsigned long offset;

	unsigned int size;

	void **pages;
@@ -2619,12 +2741,14 @@ void perf_output_copy(struct perf_output_handle *handle, 
	pages		= handle->data->data_pages;



	do {

		unsigned int page_offset;

		unsigned long page_offset;

		unsigned long page_size;

		int nr;



		nr	    = (offset >> PAGE_SHIFT) & pages_mask;

		page_offset = offset & (PAGE_SIZE - 1);

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

		page_size   = 1UL << (handle->data->data_order + PAGE_SHIFT);

		page_offset = offset & (page_size - 1);

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



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

tools/perf/design.txt

+3 −0
Original line number Diff line number Diff line
@@ -455,3 +455,6 @@ will need at least this: 


If your architecture does have hardware capabilities, you can override the

weak stub hw_perf_event_init() to register hardware counters.



Architectures that have d-cache aliassing issues, such as Sparc and ARM,

should select PERF_USE_VMALLOC in order to avoid these for perf mmap().