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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: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: David 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: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-09-21 16:08:49 +02:00 committed by Ingo Molnar
parent e13dbd7d75
commit 906010b213
5 changed files with 219 additions and 67 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/sparc/Kconfig
View File

@ -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

5
include/linux/perf_event.h
View File

@ -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 */

18
init/Kconfig
View File

@ -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

258
kernel/perf_event.c
View File

@ -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 @@ unlock:
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;
}
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;
if (vmf->flags & FAULT_FLAG_WRITE)
goto unlock;
vmf->page = virt_to_page(data->data_pages[nr]);
}
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;
return data->nr_pages << (PAGE_SHIFT + data->data_order);
}
static int perf_mmap_data_alloc(struct perf_event *event, int nr_pages)
#ifndef CONFIG_PERF_USE_VMALLOC
/*
* Back perf_mmap() with regular GFP_KERNEL-0 pages.
*/
static struct page *
perf_mmap_to_page(struct perf_mmap_data *data, unsigned long pgoff)
{
if (pgoff > data->nr_pages)
return NULL;
if (pgoff == 0)
return virt_to_page(data->user_page);
return virt_to_page(data->data_pages[pgoff - 1]);
}
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 @@ fail_user_page:
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);

3
tools/perf/design.txt
View File

@ -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().