perf: Split up buffer handling from core code

And create the internal perf events header.

v2: Keep an internal inlined perf_output_copy()

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Stephane Eranian <eranian@google.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1305827704-5607-1-git-send-email-fweisbec@gmail.com
[ v3: use clearer 'ring_buffer' and 'rb' naming ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

4 files changed, 568 insertions, 498 deletions

diff --git a/kernel/events/Makefile b/kernel/events/Makefile
index 1ce23d3d8394..89e5e8aa4c36 100644
--- a/kernel/events/Makefile
+++ b/kernel/events/Makefile
@@ -2,5 +2,5 @@ ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_core.o = -pg
 endif
 
-obj-y := core.o
+obj-y := core.o ring_buffer.o
 obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5e8c7b1389bc..5e70f62752a2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -36,6 +36,8 @@
 #include <linux/ftrace_event.h>
 #include <linux/hw_breakpoint.h>
 
+#include "internal.h"
+
 #include <asm/irq_regs.h>
 
 struct remote_function_call {
@@ -2886,7 +2888,7 @@ static void free_event_rcu(struct rcu_head *head)
         kfree(event);
 }
 
-static void perf_buffer_put(struct perf_buffer *buffer);
+static void ring_buffer_put(struct ring_buffer *rb);
 
 static void free_event(struct perf_event *event)
 {
@@ -2909,9 +2911,9 @@ static void free_event(struct perf_event *event)
                 }
         }
 
-        if (event->buffer) {
-                perf_buffer_put(event->buffer);
-                event->buffer = NULL;
+        if (event->rb) {
+                ring_buffer_put(event->rb);
+                event->rb = NULL;
         }
 
         if (is_cgroup_event(event))
@@ -3139,13 +3141,13 @@ perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 static unsigned int perf_poll(struct file *file, poll_table *wait)
 {
         struct perf_event *event = file->private_data;
-        struct perf_buffer *buffer;
+        struct ring_buffer *rb;
         unsigned int events = POLL_HUP;
 
         rcu_read_lock();
-        buffer = rcu_dereference(event->buffer);
-        if (buffer)
-                events = atomic_xchg(&buffer->poll, 0);
+        rb = rcu_dereference(event->rb);
+        if (rb)
+                events = atomic_xchg(&rb->poll, 0);
         rcu_read_unlock();
 
         poll_wait(file, &event->waitq, wait);
@@ -3356,14 +3358,14 @@ static int perf_event_index(struct perf_event *event)
 void perf_event_update_userpage(struct perf_event *event)
 {
         struct perf_event_mmap_page *userpg;
-        struct perf_buffer *buffer;
+        struct ring_buffer *rb;
 
         rcu_read_lock();
-        buffer = rcu_dereference(event->buffer);
-        if (!buffer)
+        rb = rcu_dereference(event->rb);
+        if (!rb)
                 goto unlock;
 
-        userpg = buffer->user_page;
+        userpg = rb->user_page;
 
         /*
          * Disable preemption so as to not let the corresponding user-space
@@ -3390,220 +3392,10 @@ unlock:
         rcu_read_unlock();
 }
 
-static unsigned long perf_data_size(struct perf_buffer *buffer);
-
-static void
-perf_buffer_init(struct perf_buffer *buffer, long watermark, int flags)
-{
-        long max_size = perf_data_size(buffer);
-
-        if (watermark)
-                buffer->watermark = min(max_size, watermark);
-
-        if (!buffer->watermark)
-                buffer->watermark = max_size / 2;
-
-        if (flags & PERF_BUFFER_WRITABLE)
-                buffer->writable = 1;
-
-        atomic_set(&buffer->refcount, 1);
-}
-
-#ifndef CONFIG_PERF_USE_VMALLOC
-
-/*
- * Back perf_mmap() with regular GFP_KERNEL-0 pages.
- */
-
-static struct page *
-perf_mmap_to_page(struct perf_buffer *buffer, unsigned long pgoff)
-{
-        if (pgoff > buffer->nr_pages)
-                return NULL;
-
-        if (pgoff == 0)
-                return virt_to_page(buffer->user_page);
-
-        return virt_to_page(buffer->data_pages[pgoff - 1]);
-}
-
-static void *perf_mmap_alloc_page(int cpu)
-{
-        struct page *page;
-        int node;
-
-        node = (cpu == -1) ? cpu : cpu_to_node(cpu);
-        page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
-        if (!page)
-                return NULL;
-
-        return page_address(page);
-}
-
-static struct perf_buffer *
-perf_buffer_alloc(int nr_pages, long watermark, int cpu, int flags)
-{
-        struct perf_buffer *buffer;
-        unsigned long size;
-        int i;
-
-        size = sizeof(struct perf_buffer);
-        size += nr_pages * sizeof(void *);
-
-        buffer = kzalloc(size, GFP_KERNEL);
-        if (!buffer)
-                goto fail;
-
-        buffer->user_page = perf_mmap_alloc_page(cpu);
-        if (!buffer->user_page)
-                goto fail_user_page;
-
-        for (i = 0; i < nr_pages; i++) {
-                buffer->data_pages[i] = perf_mmap_alloc_page(cpu);
-                if (!buffer->data_pages[i])
-                        goto fail_data_pages;
-        }
-
-        buffer->nr_pages = nr_pages;
-
-        perf_buffer_init(buffer, watermark, flags);
-
-        return buffer;
-
-fail_data_pages:
-        for (i--; i >= 0; i--)
-                free_page((unsigned long)buffer->data_pages[i]);
-
-        free_page((unsigned long)buffer->user_page);
-
-fail_user_page:
-        kfree(buffer);
-
-fail:
-        return NULL;
-}
-
-static void perf_mmap_free_page(unsigned long addr)
-{
-        struct page *page = virt_to_page((void *)addr);
-
-        page->mapping = NULL;
-        __free_page(page);
-}
-
-static void perf_buffer_free(struct perf_buffer *buffer)
-{
-        int i;
-
-        perf_mmap_free_page((unsigned long)buffer->user_page);
-        for (i = 0; i < buffer->nr_pages; i++)
-                perf_mmap_free_page((unsigned long)buffer->data_pages[i]);
-        kfree(buffer);
-}
-
-static inline int page_order(struct perf_buffer *buffer)
-{
-        return 0;
-}
-
-#else
-
-/*
- * Back perf_mmap() with vmalloc memory.
- *
- * Required for architectures that have d-cache aliasing issues.
- */
-
-static inline int page_order(struct perf_buffer *buffer)
-{
-        return buffer->page_order;
-}
-
-static struct page *
-perf_mmap_to_page(struct perf_buffer *buffer, unsigned long pgoff)
-{
-        if (pgoff > (1UL << page_order(buffer)))
-                return NULL;
-
-        return vmalloc_to_page((void *)buffer->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_buffer_free_work(struct work_struct *work)
-{
-        struct perf_buffer *buffer;
-        void *base;
-        int i, nr;
-
-        buffer = container_of(work, struct perf_buffer, work);
-        nr = 1 << page_order(buffer);
-
-        base = buffer->user_page;
-        for (i = 0; i < nr + 1; i++)
-                perf_mmap_unmark_page(base + (i * PAGE_SIZE));
-
-        vfree(base);
-        kfree(buffer);
-}
-
-static void perf_buffer_free(struct perf_buffer *buffer)
-{
-        schedule_work(&buffer->work);
-}
-
-static struct perf_buffer *
-perf_buffer_alloc(int nr_pages, long watermark, int cpu, int flags)
-{
-        struct perf_buffer *buffer;
-        unsigned long size;
-        void *all_buf;
-
-        size = sizeof(struct perf_buffer);
-        size += sizeof(void *);
-
-        buffer = kzalloc(size, GFP_KERNEL);
-        if (!buffer)
-                goto fail;
-
-        INIT_WORK(&buffer->work, perf_buffer_free_work);
-
-        all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
-        if (!all_buf)
-                goto fail_all_buf;
-
-        buffer->user_page = all_buf;
-        buffer->data_pages[0] = all_buf + PAGE_SIZE;
-        buffer->page_order = ilog2(nr_pages);
-        buffer->nr_pages = 1;
-
-        perf_buffer_init(buffer, watermark, flags);
-
-        return buffer;
-
-fail_all_buf:
-        kfree(buffer);
-
-fail:
-        return NULL;
-}
-
-#endif
-
-static unsigned long perf_data_size(struct perf_buffer *buffer)
-{
-        return buffer->nr_pages << (PAGE_SHIFT + page_order(buffer));
-}
-
 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_buffer *buffer;
+        struct ring_buffer *rb;
         int ret = VM_FAULT_SIGBUS;
 
         if (vmf->flags & FAULT_FLAG_MKWRITE) {
@@ -3613,14 +3405,14 @@ static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
         }
 
         rcu_read_lock();
-        buffer = rcu_dereference(event->buffer);
-        if (!buffer)
+        rb = rcu_dereference(event->rb);
+        if (!rb)
                 goto unlock;
 
         if (vmf->pgoff && (vmf->flags & FAULT_FLAG_WRITE))
                 goto unlock;
 
-        vmf->page = perf_mmap_to_page(buffer, vmf->pgoff);
+        vmf->page = perf_mmap_to_page(rb, vmf->pgoff);
         if (!vmf->page)
                 goto unlock;
 
@@ -3635,35 +3427,35 @@ unlock:
         return ret;
 }
 
-static void perf_buffer_free_rcu(struct rcu_head *rcu_head)
+static void rb_free_rcu(struct rcu_head *rcu_head)
 {
-        struct perf_buffer *buffer;
+        struct ring_buffer *rb;
 
-        buffer = container_of(rcu_head, struct perf_buffer, rcu_head);
-        perf_buffer_free(buffer);
+        rb = container_of(rcu_head, struct ring_buffer, rcu_head);
+        rb_free(rb);
 }
 
-static struct perf_buffer *perf_buffer_get(struct perf_event *event)
+static struct ring_buffer *ring_buffer_get(struct perf_event *event)
 {
-        struct perf_buffer *buffer;
+        struct ring_buffer *rb;
 
         rcu_read_lock();
-        buffer = rcu_dereference(event->buffer);
-        if (buffer) {
-                if (!atomic_inc_not_zero(&buffer->refcount))
-                        buffer = NULL;
+        rb = rcu_dereference(event->rb);
+        if (rb) {
+                if (!atomic_inc_not_zero(&rb->refcount))
+                        rb = NULL;
         }
         rcu_read_unlock();
 
-        return buffer;
+        return rb;
 }
 
-static void perf_buffer_put(struct perf_buffer *buffer)
+static void ring_buffer_put(struct ring_buffer *rb)
 {
-        if (!atomic_dec_and_test(&buffer->refcount))
+        if (!atomic_dec_and_test(&rb->refcount))
                 return;
 
-        call_rcu(&buffer->rcu_head, perf_buffer_free_rcu);
+        call_rcu(&rb->rcu_head, rb_free_rcu);
 }
 
 static void perf_mmap_open(struct vm_area_struct *vma)
@@ -3678,16 +3470,16 @@ static void perf_mmap_close(struct vm_area_struct *vma)
         struct perf_event *event = vma->vm_file->private_data;
 
         if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) {
-                unsigned long size = perf_data_size(event->buffer);
+                unsigned long size = perf_data_size(event->rb);
                 struct user_struct *user = event->mmap_user;
-                struct perf_buffer *buffer = event->buffer;
+                struct ring_buffer *rb = event->rb;
 
                 atomic_long_sub((size >> PAGE_SHIFT) + 1, &user->locked_vm);
                 vma->vm_mm->locked_vm -= event->mmap_locked;
-                rcu_assign_pointer(event->buffer, NULL);
+                rcu_assign_pointer(event->rb, NULL);
                 mutex_unlock(&event->mmap_mutex);
 
-                perf_buffer_put(buffer);
+                ring_buffer_put(rb);
                 free_uid(user);
         }
 }
@@ -3705,7 +3497,7 @@ 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_buffer *buffer;
+        struct ring_buffer *rb;
         unsigned long vma_size;
         unsigned long nr_pages;
         long user_extra, extra;
@@ -3714,7 +3506,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
         /*
          * Don't allow mmap() of inherited per-task counters. This would
          * create a performance issue due to all children writing to the
-         * same buffer.
+         * same rb.
          */
         if (event->cpu == -1 && event->attr.inherit)
                 return -EINVAL;
@@ -3726,7 +3518,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
         nr_pages = (vma_size / PAGE_SIZE) - 1;
 
         /*
-         * If we have buffer pages ensure they're a power-of-two number, so we
+         * If we have rb pages ensure they're a power-of-two number, so we
          * can do bitmasks instead of modulo.
          */
         if (nr_pages != 0 && !is_power_of_2(nr_pages))
@@ -3740,9 +3532,9 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 
         WARN_ON_ONCE(event->ctx->parent_ctx);
         mutex_lock(&event->mmap_mutex);
-        if (event->buffer) {
-                if (event->buffer->nr_pages == nr_pages)
-                        atomic_inc(&event->buffer->refcount);
+        if (event->rb) {
+                if (event->rb->nr_pages == nr_pages)
+                        atomic_inc(&event->rb->refcount);
                 else
                         ret = -EINVAL;
                 goto unlock;
@@ -3772,18 +3564,18 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
                 goto unlock;
         }
 
-        WARN_ON(event->buffer);
+        WARN_ON(event->rb);
 
         if (vma->vm_flags & VM_WRITE)
-                flags |= PERF_BUFFER_WRITABLE;
+                flags |= RING_BUFFER_WRITABLE;
 
-        buffer = perf_buffer_alloc(nr_pages, event->attr.wakeup_watermark,
+        rb = rb_alloc(nr_pages, event->attr.wakeup_watermark,
                                    event->cpu, flags);
-        if (!buffer) {
+        if (!rb) {
                 ret = -ENOMEM;
                 goto unlock;
         }
-        rcu_assign_pointer(event->buffer, buffer);
+        rcu_assign_pointer(event->rb, rb);
 
         atomic_long_add(user_extra, &user->locked_vm);
         event->mmap_locked = extra;
@@ -3882,117 +3674,6 @@ int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
 }
 EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);
 
-/*
- * Output
- */
-static bool perf_output_space(struct perf_buffer *buffer, unsigned long tail,
-                              unsigned long offset, unsigned long head)
-{
-        unsigned long mask;
-
-        if (!buffer->writable)
-                return true;
-
-        mask = perf_data_size(buffer) - 1;
-
-        offset = (offset - tail) & mask;
-        head   = (head   - tail) & mask;
-
-        if ((int)(head - offset) < 0)
-                return false;
-
-        return true;
-}
-
-static void perf_output_wakeup(struct perf_output_handle *handle)
-{
-        atomic_set(&handle->buffer->poll, POLL_IN);
-
-        if (handle->nmi) {
-                handle->event->pending_wakeup = 1;
-                irq_work_queue(&handle->event->pending);
-        } else
-                perf_event_wakeup(handle->event);
-}
-
-/*
- * We need to ensure a later event_id doesn't publish a head when a former
- * event isn't done writing. However since we need to deal with NMIs we
- * cannot fully serialize things.
- *
- * We only publish the head (and generate a wakeup) when the outer-most
- * event completes.
- */
-static void perf_output_get_handle(struct perf_output_handle *handle)
-{
-        struct perf_buffer *buffer = handle->buffer;
-
-        preempt_disable();
-        local_inc(&buffer->nest);
-        handle->wakeup = local_read(&buffer->wakeup);
-}
-
-static void perf_output_put_handle(struct perf_output_handle *handle)
-{
-        struct perf_buffer *buffer = handle->buffer;
-        unsigned long head;
-
-again:
-        head = local_read(&buffer->head);
-
-        /*
-         * IRQ/NMI can happen here, which means we can miss a head update.
-         */
-
-        if (!local_dec_and_test(&buffer->nest))
-                goto out;
-
-        /*
-         * Publish the known good head. Rely on the full barrier implied
-         * by atomic_dec_and_test() order the buffer->head read and this
-         * write.
-         */
-        buffer->user_page->data_head = head;
-
-        /*
-         * Now check if we missed an update, rely on the (compiler)
-         * barrier in atomic_dec_and_test() to re-read buffer->head.
-         */
-        if (unlikely(head != local_read(&buffer->head))) {
-                local_inc(&buffer->nest);
-                goto again;
-        }
-
-        if (handle->wakeup != local_read(&buffer->wakeup))
-                perf_output_wakeup(handle);
-
-out:
-        preempt_enable();
-}
-
-__always_inline void perf_output_copy(struct perf_output_handle *handle,
-                      const void *buf, unsigned int len)
-{
-        do {
-                unsigned long size = min_t(unsigned long, handle->size, len);
-
-                memcpy(handle->addr, buf, size);
-
-                len -= size;
-                handle->addr += size;
-                buf += size;
-                handle->size -= size;
-                if (!handle->size) {
-                        struct perf_buffer *buffer = handle->buffer;
-
-                        handle->page++;
-                        handle->page &= buffer->nr_pages - 1;
-                        handle->addr = buffer->data_pages[handle->page];
-                        handle->size = PAGE_SIZE << page_order(buffer);
-                }
-        } while (len);
-}
-
 static void __perf_event_header__init_id(struct perf_event_header *header,
                                          struct perf_sample_data *data,
                                          struct perf_event *event)
@@ -4023,9 +3704,9 @@ static void __perf_event_header__init_id(struct perf_event_header *header,
         }
 }
 
-static void perf_event_header__init_id(struct perf_event_header *header,
-                                       struct perf_sample_data *data,
-                                       struct perf_event *event)
+void perf_event_header__init_id(struct perf_event_header *header,
+                                struct perf_sample_data *data,
+                                struct perf_event *event)
 {
         if (event->attr.sample_id_all)
                 __perf_event_header__init_id(header, data, event);
@@ -4052,121 +3733,14 @@ static void __perf_event__output_id_sample(struct perf_output_handle *handle,
                 perf_output_put(handle, data->cpu_entry);
 }
 
-static void perf_event__output_id_sample(struct perf_event *event,
-                                         struct perf_output_handle *handle,
-                                         struct perf_sample_data *sample)
+void perf_event__output_id_sample(struct perf_event *event,
+                                  struct perf_output_handle *handle,
+                                  struct perf_sample_data *sample)
 {
         if (event->attr.sample_id_all)
                 __perf_event__output_id_sample(handle, sample);
 }
 
-int perf_output_begin(struct perf_output_handle *handle,
-                      struct perf_event *event, unsigned int size,
-                      int nmi, int sample)
-{
-        struct perf_buffer *buffer;
-        unsigned long tail, offset, head;
-        int have_lost;
-        struct perf_sample_data sample_data;
-        struct {
-                struct perf_event_header header;
-                u64                      id;
-                u64                      lost;
-        } lost_event;
-
-        rcu_read_lock();
-        /*
-         * For inherited events we send all the output towards the parent.
-         */
-        if (event->parent)
-                event = event->parent;
-
-        buffer = rcu_dereference(event->buffer);
-        if (!buffer)
-                goto out;
-
-        handle->buffer  = buffer;
-        handle->event   = event;
-        handle->nmi     = nmi;
-        handle->sample  = sample;
-
-        if (!buffer->nr_pages)
-                goto out;
-
-        have_lost = local_read(&buffer->lost);
-        if (have_lost) {
-                lost_event.header.size = sizeof(lost_event);
-                perf_event_header__init_id(&lost_event.header, &sample_data,
-                                           event);
-                size += lost_event.header.size;
-        }
-
-        perf_output_get_handle(handle);
-
-        do {
-                /*
-                 * Userspace could choose to issue a mb() before updating the
-                 * tail pointer. So that all reads will be completed before the
-                 * write is issued.
-                 */
-                tail = ACCESS_ONCE(buffer->user_page->data_tail);
-                smp_rmb();
-                offset = head = local_read(&buffer->head);
-                head += size;
-                if (unlikely(!perf_output_space(buffer, tail, offset, head)))
-                        goto fail;
-        } while (local_cmpxchg(&buffer->head, offset, head) != offset);
-
-        if (head - local_read(&buffer->wakeup) > buffer->watermark)
-                local_add(buffer->watermark, &buffer->wakeup);
-
-        handle->page = offset >> (PAGE_SHIFT + page_order(buffer));
-        handle->page &= buffer->nr_pages - 1;
-        handle->size = offset & ((PAGE_SIZE << page_order(buffer)) - 1);
-        handle->addr = buffer->data_pages[handle->page];
-        handle->addr += handle->size;
-        handle->size = (PAGE_SIZE << page_order(buffer)) - handle->size;
-
-        if (have_lost) {
-                lost_event.header.type = PERF_RECORD_LOST;
-                lost_event.header.misc = 0;
-                lost_event.id          = event->id;
-                lost_event.lost        = local_xchg(&buffer->lost, 0);
-
-                perf_output_put(handle, lost_event);
-                perf_event__output_id_sample(event, handle, &sample_data);
-        }
-
-        return 0;
-
-fail:
-        local_inc(&buffer->lost);
-        perf_output_put_handle(handle);
-out:
-        rcu_read_unlock();
-
-        return -ENOSPC;
-}
-
-void perf_output_end(struct perf_output_handle *handle)
-{
-        struct perf_event *event = handle->event;
-        struct perf_buffer *buffer = handle->buffer;
-
-        int wakeup_events = event->attr.wakeup_events;
-
-        if (handle->sample && wakeup_events) {
-                int events = local_inc_return(&buffer->events);
-                if (events >= wakeup_events) {
-                        local_sub(wakeup_events, &buffer->events);
-                        local_inc(&buffer->wakeup);
-                }
-        }
-
-        perf_output_put_handle(handle);
-        rcu_read_unlock();
-}
-
 static void perf_output_read_one(struct perf_output_handle *handle,
                                  struct perf_event *event,
                                  u64 enabled, u64 running)
@@ -4187,7 +3761,7 @@ static void perf_output_read_one(struct perf_output_handle *handle,
         if (read_format & PERF_FORMAT_ID)
                 values[n++] = primary_event_id(event);
 
-        perf_output_copy(handle, values, n * sizeof(u64));
+        __output_copy(handle, values, n * sizeof(u64));
 }
 
 /*
@@ -4217,7 +3791,7 @@ static void perf_output_read_group(struct perf_output_handle *handle,
         if (read_format & PERF_FORMAT_ID)
                 values[n++] = primary_event_id(leader);
 
-        perf_output_copy(handle, values, n * sizeof(u64));
+        __output_copy(handle, values, n * sizeof(u64));
 
         list_for_each_entry(sub, &leader->sibling_list, group_entry) {
                 n = 0;
@@ -4229,7 +3803,7 @@ static void perf_output_read_group(struct perf_output_handle *handle,
                 if (read_format & PERF_FORMAT_ID)
                         values[n++] = primary_event_id(sub);
 
-                perf_output_copy(handle, values, n * sizeof(u64));
+                __output_copy(handle, values, n * sizeof(u64));
         }
 }
 
@@ -4309,7 +3883,7 @@ void perf_output_sample(struct perf_output_handle *handle,
 
                         size *= sizeof(u64);
 
-                        perf_output_copy(handle, data->callchain, size);
+                        __output_copy(handle, data->callchain, size);
                 } else {
                         u64 nr = 0;
                         perf_output_put(handle, nr);
@@ -4319,8 +3893,8 @@ void perf_output_sample(struct perf_output_handle *handle,
         if (sample_type & PERF_SAMPLE_RAW) {
                 if (data->raw) {
                         perf_output_put(handle, data->raw->size);
-                        perf_output_copy(handle, data->raw->data,
-                                         data->raw->size);
+                        __output_copy(handle, data->raw->data,
+                                           data->raw->size);
                 } else {
                         struct {
                                 u32     size;
@@ -4617,7 +4191,7 @@ static void perf_event_comm_output(struct perf_event *event,
         comm_event->event_id.tid = perf_event_tid(event, comm_event->task);
 
         perf_output_put(&handle, comm_event->event_id);
-        perf_output_copy(&handle, comm_event->comm,
+        __output_copy(&handle, comm_event->comm,
                                    comm_event->comm_size);
 
         perf_event__output_id_sample(event, &handle, &sample);
@@ -4763,7 +4337,7 @@ static void perf_event_mmap_output(struct perf_event *event,
         mmap_event->event_id.tid = perf_event_tid(event, current);
 
         perf_output_put(&handle, mmap_event->event_id);
-        perf_output_copy(&handle, mmap_event->file_name,
+        __output_copy(&handle, mmap_event->file_name,
                                    mmap_event->file_size);
 
         perf_event__output_id_sample(event, &handle, &sample);
@@ -4819,7 +4393,7 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
 
         if (file) {
                 /*
-                 * d_path works from the end of the buffer backwards, so we
+                 * d_path works from the end of the rb backwards, so we
                  * need to add enough zero bytes after the string to handle
                  * the 64bit alignment we do later.
                  */
@@ -6346,7 +5920,7 @@ err_size:
 static int
 perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
 {
-        struct perf_buffer *buffer = NULL, *old_buffer = NULL;
+        struct ring_buffer *rb = NULL, *old_rb = NULL;
         int ret = -EINVAL;
 
         if (!output_event)
@@ -6363,7 +5937,7 @@ perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
                 goto out;
 
         /*
-         * If its not a per-cpu buffer, it must be the same task.
+         * If its not a per-cpu rb, it must be the same task.
          */
         if (output_event->cpu == -1 && output_event->ctx != event->ctx)
                 goto out;
@@ -6375,20 +5949,20 @@ set:
                 goto unlock;
 
         if (output_event) {
-                /* get the buffer we want to redirect to */
-                buffer = perf_buffer_get(output_event);
-                if (!buffer)
+                /* get the rb we want to redirect to */
+                rb = ring_buffer_get(output_event);
+                if (!rb)
                         goto unlock;
         }
 
-        old_buffer = event->buffer;
-        rcu_assign_pointer(event->buffer, buffer);
+        old_rb = event->rb;
+        rcu_assign_pointer(event->rb, rb);
         ret = 0;
 unlock:
         mutex_unlock(&event->mmap_mutex);
 
-        if (old_buffer)
-                perf_buffer_put(old_buffer);
+        if (old_rb)
+                ring_buffer_put(old_rb);
 out:
         return ret;
 }
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
new file mode 100644
index 000000000000..114f27f3a624
--- /dev/null
+++ b/kernel/events/internal.h
@@ -0,0 +1,97 @@
+#ifndef _KERNEL_EVENTS_INTERNAL_H
+#define _KERNEL_EVENTS_INTERNAL_H
+
+#define RING_BUFFER_WRITABLE            0x01
+
+struct ring_buffer {
+        atomic_t                        refcount;
+        struct rcu_head                 rcu_head;
+#ifdef CONFIG_PERF_USE_VMALLOC
+        struct work_struct              work;
+        int                             page_order;     /* allocation order  */
+#endif
+        int                             nr_pages;       /* nr of data pages  */
+        int                             writable;       /* are we writable   */
+
+        atomic_t                        poll;           /* POLL_ for wakeups */
+
+        local_t                         head;           /* write position    */
+        local_t                         nest;           /* nested writers    */
+        local_t                         events;         /* event limit       */
+        local_t                         wakeup;         /* wakeup stamp      */
+        local_t                         lost;           /* nr records lost   */
+
+        long                            watermark;      /* wakeup watermark  */
+
+        struct perf_event_mmap_page     *user_page;
+        void                            *data_pages[0];
+};
+
+
+extern void rb_free(struct ring_buffer *rb);
+extern struct ring_buffer *
+rb_alloc(int nr_pages, long watermark, int cpu, int flags);
+extern void perf_event_wakeup(struct perf_event *event);
+
+extern void
+perf_event_header__init_id(struct perf_event_header *header,
+                           struct perf_sample_data *data,
+                           struct perf_event *event);
+extern void
+perf_event__output_id_sample(struct perf_event *event,
+                             struct perf_output_handle *handle,
+                             struct perf_sample_data *sample);
+
+extern struct page *
+perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff);
+
+#ifdef CONFIG_PERF_USE_VMALLOC
+/*
+ * Back perf_mmap() with vmalloc memory.
+ *
+ * Required for architectures that have d-cache aliasing issues.
+ */
+
+static inline int page_order(struct ring_buffer *rb)
+{
+        return rb->page_order;
+}
+
+#else
+
+static inline int page_order(struct ring_buffer *rb)
+{
+        return 0;
+}
+#endif
+
+static unsigned long perf_data_size(struct ring_buffer *rb)
+{
+        return rb->nr_pages << (PAGE_SHIFT + page_order(rb));
+}
+
+static inline void
+__output_copy(struct perf_output_handle *handle,
+                   const void *buf, unsigned int len)
+{
+        do {
+                unsigned long size = min_t(unsigned long, handle->size, len);
+
+                memcpy(handle->addr, buf, size);
+
+                len -= size;
+                handle->addr += size;
+                buf += size;
+                handle->size -= size;
+                if (!handle->size) {
+                        struct ring_buffer *rb = handle->rb;
+
+                        handle->page++;
+                        handle->page &= rb->nr_pages - 1;
+                        handle->addr = rb->data_pages[handle->page];
+                        handle->size = PAGE_SIZE << page_order(rb);
+                }
+        } while (len);
+}
+
+#endif /* _KERNEL_EVENTS_INTERNAL_H */
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
new file mode 100644
index 000000000000..fde52595d8f7
--- /dev/null
+++ b/kernel/events/ring_buffer.c
@@ -0,0 +1,399 @@
+/*
+ * Performance events ring-buffer code:
+ *
+ *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
+ *  Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
+ *  Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
+ *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
+ *
+ * For licensing details see kernel-base/COPYING
+ */
+
+#include <linux/perf_event.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+
+#include "internal.h"
+
+static bool perf_output_space(struct ring_buffer *rb, unsigned long tail,
+                              unsigned long offset, unsigned long head)
+{
+        unsigned long mask;
+
+        if (!rb->writable)
+                return true;
+
+        mask = perf_data_size(rb) - 1;
+
+        offset = (offset - tail) & mask;
+        head   = (head   - tail) & mask;
+
+        if ((int)(head - offset) < 0)
+                return false;
+
+        return true;
+}
+
+static void perf_output_wakeup(struct perf_output_handle *handle)
+{
+        atomic_set(&handle->rb->poll, POLL_IN);
+
+        if (handle->nmi) {
+                handle->event->pending_wakeup = 1;
+                irq_work_queue(&handle->event->pending);
+        } else
+                perf_event_wakeup(handle->event);
+}
+
+/*
+ * We need to ensure a later event_id doesn't publish a head when a former
+ * event isn't done writing. However since we need to deal with NMIs we
+ * cannot fully serialize things.
+ *
+ * We only publish the head (and generate a wakeup) when the outer-most
+ * event completes.
+ */
+static void perf_output_get_handle(struct perf_output_handle *handle)
+{
+        struct ring_buffer *rb = handle->rb;
+
+        preempt_disable();
+        local_inc(&rb->nest);
+        handle->wakeup = local_read(&rb->wakeup);
+}
+
+static void perf_output_put_handle(struct perf_output_handle *handle)
+{
+        struct ring_buffer *rb = handle->rb;
+        unsigned long head;
+
+again:
+        head = local_read(&rb->head);
+
+        /*
+         * IRQ/NMI can happen here, which means we can miss a head update.
+         */
+
+        if (!local_dec_and_test(&rb->nest))
+                goto out;
+
+        /*
+         * Publish the known good head. Rely on the full barrier implied
+         * by atomic_dec_and_test() order the rb->head read and this
+         * write.
+         */
+        rb->user_page->data_head = head;
+
+        /*
+         * Now check if we missed an update, rely on the (compiler)
+         * barrier in atomic_dec_and_test() to re-read rb->head.
+         */
+        if (unlikely(head != local_read(&rb->head))) {
+                local_inc(&rb->nest);
+                goto again;
+        }
+
+        if (handle->wakeup != local_read(&rb->wakeup))
+                perf_output_wakeup(handle);
+
+out:
+        preempt_enable();
+}
+
+int perf_output_begin(struct perf_output_handle *handle,
+                      struct perf_event *event, unsigned int size,
+                      int nmi, int sample)
+{
+        struct ring_buffer *rb;
+        unsigned long tail, offset, head;
+        int have_lost;
+        struct perf_sample_data sample_data;
+        struct {
+                struct perf_event_header header;
+                u64                      id;
+                u64                      lost;
+        } lost_event;
+
+        rcu_read_lock();
+        /*
+         * For inherited events we send all the output towards the parent.
+         */
+        if (event->parent)
+                event = event->parent;
+
+        rb = rcu_dereference(event->rb);
+        if (!rb)
+                goto out;
+
+        handle->rb      = rb;
+        handle->event   = event;
+        handle->nmi     = nmi;
+        handle->sample  = sample;
+
+        if (!rb->nr_pages)
+                goto out;
+
+        have_lost = local_read(&rb->lost);
+        if (have_lost) {
+                lost_event.header.size = sizeof(lost_event);
+                perf_event_header__init_id(&lost_event.header, &sample_data,
+                                           event);
+                size += lost_event.header.size;
+        }
+
+        perf_output_get_handle(handle);
+
+        do {
+                /*
+                 * Userspace could choose to issue a mb() before updating the
+                 * tail pointer. So that all reads will be completed before the
+                 * write is issued.
+                 */
+                tail = ACCESS_ONCE(rb->user_page->data_tail);
+                smp_rmb();
+                offset = head = local_read(&rb->head);
+                head += size;
+                if (unlikely(!perf_output_space(rb, tail, offset, head)))
+                        goto fail;
+        } while (local_cmpxchg(&rb->head, offset, head) != offset);
+
+        if (head - local_read(&rb->wakeup) > rb->watermark)
+                local_add(rb->watermark, &rb->wakeup);
+
+        handle->page = offset >> (PAGE_SHIFT + page_order(rb));
+        handle->page &= rb->nr_pages - 1;
+        handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1);
+        handle->addr = rb->data_pages[handle->page];
+        handle->addr += handle->size;
+        handle->size = (PAGE_SIZE << page_order(rb)) - handle->size;
+
+        if (have_lost) {
+                lost_event.header.type = PERF_RECORD_LOST;
+                lost_event.header.misc = 0;
+                lost_event.id          = event->id;
+                lost_event.lost        = local_xchg(&rb->lost, 0);
+
+                perf_output_put(handle, lost_event);
+                perf_event__output_id_sample(event, handle, &sample_data);
+        }
+
+        return 0;
+
+fail:
+        local_inc(&rb->lost);
+        perf_output_put_handle(handle);
+out:
+        rcu_read_unlock();
+
+        return -ENOSPC;
+}
+
+void perf_output_copy(struct perf_output_handle *handle,
+                      const void *buf, unsigned int len)
+{
+        __output_copy(handle, buf, len);
+}
+
+void perf_output_end(struct perf_output_handle *handle)
+{
+        struct perf_event *event = handle->event;
+        struct ring_buffer *rb = handle->rb;
+
+        int wakeup_events = event->attr.wakeup_events;
+
+        if (handle->sample && wakeup_events) {
+                int events = local_inc_return(&rb->events);
+                if (events >= wakeup_events) {
+                        local_sub(wakeup_events, &rb->events);
+                        local_inc(&rb->wakeup);
+                }
+        }
+
+        perf_output_put_handle(handle);
+        rcu_read_unlock();
+}
+
+static void
+ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
+{
+        long max_size = perf_data_size(rb);
+
+        if (watermark)
+                rb->watermark = min(max_size, watermark);
+
+        if (!rb->watermark)
+                rb->watermark = max_size / 2;
+
+        if (flags & RING_BUFFER_WRITABLE)
+                rb->writable = 1;
+
+        atomic_set(&rb->refcount, 1);
+}
+
+#ifndef CONFIG_PERF_USE_VMALLOC
+
+/*
+ * Back perf_mmap() with regular GFP_KERNEL-0 pages.
+ */
+
+struct page *
+perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
+{
+        if (pgoff > rb->nr_pages)
+                return NULL;
+
+        if (pgoff == 0)
+                return virt_to_page(rb->user_page);
+
+        return virt_to_page(rb->data_pages[pgoff - 1]);
+}
+
+static void *perf_mmap_alloc_page(int cpu)
+{
+        struct page *page;
+        int node;
+
+        node = (cpu == -1) ? cpu : cpu_to_node(cpu);
+        page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
+        if (!page)
+                return NULL;
+
+        return page_address(page);
+}
+
+struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
+{
+        struct ring_buffer *rb;
+        unsigned long size;
+        int i;
+
+        size = sizeof(struct ring_buffer);
+        size += nr_pages * sizeof(void *);
+
+        rb = kzalloc(size, GFP_KERNEL);
+        if (!rb)
+                goto fail;
+
+        rb->user_page = perf_mmap_alloc_page(cpu);
+        if (!rb->user_page)
+                goto fail_user_page;
+
+        for (i = 0; i < nr_pages; i++) {
+                rb->data_pages[i] = perf_mmap_alloc_page(cpu);
+                if (!rb->data_pages[i])
+                        goto fail_data_pages;
+        }
+
+        rb->nr_pages = nr_pages;
+
+        ring_buffer_init(rb, watermark, flags);
+
+        return rb;
+
+fail_data_pages:
+        for (i--; i >= 0; i--)
+                free_page((unsigned long)rb->data_pages[i]);
+
+        free_page((unsigned long)rb->user_page);
+
+fail_user_page:
+        kfree(rb);
+
+fail:
+        return NULL;
+}
+
+static void perf_mmap_free_page(unsigned long addr)
+{
+        struct page *page = virt_to_page((void *)addr);
+
+        page->mapping = NULL;
+        __free_page(page);
+}
+
+void rb_free(struct ring_buffer *rb)
+{
+        int i;
+
+        perf_mmap_free_page((unsigned long)rb->user_page);
+        for (i = 0; i < rb->nr_pages; i++)
+                perf_mmap_free_page((unsigned long)rb->data_pages[i]);
+        kfree(rb);
+}
+
+#else
+
+struct page *
+perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
+{
+        if (pgoff > (1UL << page_order(rb)))
+                return NULL;
+
+        return vmalloc_to_page((void *)rb->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 rb_free_work(struct work_struct *work)
+{
+        struct ring_buffer *rb;
+        void *base;
+        int i, nr;
+
+        rb = container_of(work, struct ring_buffer, work);
+        nr = 1 << page_order(rb);
+
+        base = rb->user_page;
+        for (i = 0; i < nr + 1; i++)
+                perf_mmap_unmark_page(base + (i * PAGE_SIZE));
+
+        vfree(base);
+        kfree(rb);
+}
+
+void rb_free(struct ring_buffer *rb)
+{
+        schedule_work(&rb->work);
+}
+
+struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
+{
+        struct ring_buffer *rb;
+        unsigned long size;
+        void *all_buf;
+
+        size = sizeof(struct ring_buffer);
+        size += sizeof(void *);
+
+        rb = kzalloc(size, GFP_KERNEL);
+        if (!rb)
+                goto fail;
+
+        INIT_WORK(&rb->work, rb_free_work);
+
+        all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
+        if (!all_buf)
+                goto fail_all_buf;
+
+        rb->user_page = all_buf;
+        rb->data_pages[0] = all_buf + PAGE_SIZE;
+        rb->page_order = ilog2(nr_pages);
+        rb->nr_pages = 1;
+
+        ring_buffer_init(rb, watermark, flags);
+
+        return rb;
+
+fail_all_buf:
+        kfree(rb);
+
+fail:
+        return NULL;
+}
+
+#endif