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>

1 files changed, 399 insertions, 0 deletions

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