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Subject[tip:perf/urgent] perf_event: Provide vmalloc() based mmap() backing
Commit-ID:  906010b2134e14a2e377decbadd357b3d0ab9c6a
Gitweb: http://git.kernel.org/tip/906010b2134e14a2e377decbadd357b3d0ab9c6a
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Mon, 21 Sep 2009 16:08:49 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 6 Oct 2009 14:21:50 +0200

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>
---
arch/sparc/Kconfig | 2 +
include/linux/perf_event.h | 5 +
init/Kconfig | 18 +++
kernel/perf_event.c | 248 +++++++++++++++++++++++++++++++++-----------
tools/perf/design.txt | 3 +
5 files changed, 214 insertions(+), 62 deletions(-)
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 97fca46..9b70a2f 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -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
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 3a9d36d..2e6d95f 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -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 */
diff --git a/init/Kconfig b/init/Kconfig
index c7bac39..09c5c64 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -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
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index e491fb0..9d0b5c6 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -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;
+ return data->nr_pages << (PAGE_SHIFT + data->data_order);
+}

- if (vmf->flags & FAULT_FLAG_WRITE)
- goto unlock;
+#ifndef CONFIG_PERF_USE_VMALLOC

- 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 @@ 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);

diff --git a/tools/perf/design.txt b/tools/perf/design.txt
index f1946d1..fdd42a8 100644
--- a/tools/perf/design.txt
+++ b/tools/perf/design.txt
@@ -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().

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