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394570b793
Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Michael Ellerman <michael@ellerman.id.au> Cc: Michael Neuling <mikey@neuling.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: james.hogan@imgtec.com Cc: Vince Weaver <vince@deater.net> Cc: Victor Kaplansky <VICTORK@il.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Anton Blanchard <anton@samba.org> Link: http://lkml.kernel.org/n/tip-9s5mze78gmlz19agt39i8rii@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
408 lines
8.7 KiB
C
408 lines
8.7 KiB
C
/*
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* Performance events ring-buffer code:
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*
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* Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
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* Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
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* Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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* Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
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*
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* For licensing details see kernel-base/COPYING
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*/
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#include <linux/perf_event.h>
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#include <linux/vmalloc.h>
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#include <linux/slab.h>
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#include <linux/circ_buf.h>
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#include "internal.h"
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static void perf_output_wakeup(struct perf_output_handle *handle)
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{
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atomic_set(&handle->rb->poll, POLL_IN);
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handle->event->pending_wakeup = 1;
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irq_work_queue(&handle->event->pending);
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}
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/*
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* We need to ensure a later event_id doesn't publish a head when a former
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* event isn't done writing. However since we need to deal with NMIs we
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* cannot fully serialize things.
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*
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* We only publish the head (and generate a wakeup) when the outer-most
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* event completes.
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*/
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static void perf_output_get_handle(struct perf_output_handle *handle)
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{
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struct ring_buffer *rb = handle->rb;
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preempt_disable();
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local_inc(&rb->nest);
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handle->wakeup = local_read(&rb->wakeup);
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}
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static void perf_output_put_handle(struct perf_output_handle *handle)
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{
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struct ring_buffer *rb = handle->rb;
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unsigned long head;
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again:
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head = local_read(&rb->head);
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/*
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* IRQ/NMI can happen here, which means we can miss a head update.
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*/
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if (!local_dec_and_test(&rb->nest))
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goto out;
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/*
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* Since the mmap() consumer (userspace) can run on a different CPU:
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*
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* kernel user
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*
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* READ ->data_tail READ ->data_head
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* smp_mb() (A) smp_rmb() (C)
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* WRITE $data READ $data
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* smp_wmb() (B) smp_mb() (D)
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* STORE ->data_head WRITE ->data_tail
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*
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* Where A pairs with D, and B pairs with C.
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*
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* I don't think A needs to be a full barrier because we won't in fact
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* write data until we see the store from userspace. So we simply don't
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* issue the data WRITE until we observe it. Be conservative for now.
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*
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* OTOH, D needs to be a full barrier since it separates the data READ
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* from the tail WRITE.
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*
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* For B a WMB is sufficient since it separates two WRITEs, and for C
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* an RMB is sufficient since it separates two READs.
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*
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* See perf_output_begin().
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*/
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smp_wmb();
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rb->user_page->data_head = head;
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/*
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* Now check if we missed an update -- rely on previous implied
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* compiler barriers to force a re-read.
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*/
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if (unlikely(head != local_read(&rb->head))) {
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local_inc(&rb->nest);
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goto again;
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}
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if (handle->wakeup != local_read(&rb->wakeup))
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perf_output_wakeup(handle);
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out:
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preempt_enable();
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}
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int perf_output_begin(struct perf_output_handle *handle,
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struct perf_event *event, unsigned int size)
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{
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struct ring_buffer *rb;
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unsigned long tail, offset, head;
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int have_lost, page_shift;
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struct {
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struct perf_event_header header;
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u64 id;
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u64 lost;
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} lost_event;
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rcu_read_lock();
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/*
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* For inherited events we send all the output towards the parent.
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*/
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if (event->parent)
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event = event->parent;
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rb = rcu_dereference(event->rb);
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if (unlikely(!rb))
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goto out;
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if (unlikely(!rb->nr_pages))
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goto out;
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handle->rb = rb;
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handle->event = event;
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have_lost = local_read(&rb->lost);
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if (unlikely(have_lost)) {
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size += sizeof(lost_event);
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if (event->attr.sample_id_all)
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size += event->id_header_size;
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}
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perf_output_get_handle(handle);
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do {
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tail = ACCESS_ONCE(rb->user_page->data_tail);
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offset = head = local_read(&rb->head);
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if (!rb->overwrite &&
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unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size))
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goto fail;
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head += size;
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} while (local_cmpxchg(&rb->head, offset, head) != offset);
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/*
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* Separate the userpage->tail read from the data stores below.
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* Matches the MB userspace SHOULD issue after reading the data
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* and before storing the new tail position.
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*
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* See perf_output_put_handle().
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*/
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smp_mb();
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if (unlikely(head - local_read(&rb->wakeup) > rb->watermark))
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local_add(rb->watermark, &rb->wakeup);
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page_shift = PAGE_SHIFT + page_order(rb);
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handle->page = (offset >> page_shift) & (rb->nr_pages - 1);
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offset &= (1UL << page_shift) - 1;
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handle->addr = rb->data_pages[handle->page] + offset;
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handle->size = (1UL << page_shift) - offset;
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if (unlikely(have_lost)) {
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struct perf_sample_data sample_data;
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lost_event.header.size = sizeof(lost_event);
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lost_event.header.type = PERF_RECORD_LOST;
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lost_event.header.misc = 0;
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lost_event.id = event->id;
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lost_event.lost = local_xchg(&rb->lost, 0);
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perf_event_header__init_id(&lost_event.header,
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&sample_data, event);
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perf_output_put(handle, lost_event);
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perf_event__output_id_sample(event, handle, &sample_data);
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}
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return 0;
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fail:
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local_inc(&rb->lost);
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perf_output_put_handle(handle);
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out:
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rcu_read_unlock();
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return -ENOSPC;
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}
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unsigned int perf_output_copy(struct perf_output_handle *handle,
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const void *buf, unsigned int len)
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{
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return __output_copy(handle, buf, len);
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}
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unsigned int perf_output_skip(struct perf_output_handle *handle,
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unsigned int len)
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{
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return __output_skip(handle, NULL, len);
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}
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void perf_output_end(struct perf_output_handle *handle)
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{
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perf_output_put_handle(handle);
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rcu_read_unlock();
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}
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static void
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ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
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{
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long max_size = perf_data_size(rb);
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if (watermark)
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rb->watermark = min(max_size, watermark);
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if (!rb->watermark)
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rb->watermark = max_size / 2;
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if (flags & RING_BUFFER_WRITABLE)
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rb->overwrite = 0;
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else
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rb->overwrite = 1;
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atomic_set(&rb->refcount, 1);
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INIT_LIST_HEAD(&rb->event_list);
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spin_lock_init(&rb->event_lock);
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}
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#ifndef CONFIG_PERF_USE_VMALLOC
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/*
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* Back perf_mmap() with regular GFP_KERNEL-0 pages.
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*/
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struct page *
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perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
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{
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if (pgoff > rb->nr_pages)
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return NULL;
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if (pgoff == 0)
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return virt_to_page(rb->user_page);
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return virt_to_page(rb->data_pages[pgoff - 1]);
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}
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static void *perf_mmap_alloc_page(int cpu)
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{
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struct page *page;
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int node;
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node = (cpu == -1) ? cpu : cpu_to_node(cpu);
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page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
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if (!page)
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return NULL;
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return page_address(page);
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}
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struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
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{
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struct ring_buffer *rb;
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unsigned long size;
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int i;
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size = sizeof(struct ring_buffer);
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size += nr_pages * sizeof(void *);
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rb = kzalloc(size, GFP_KERNEL);
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if (!rb)
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goto fail;
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rb->user_page = perf_mmap_alloc_page(cpu);
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if (!rb->user_page)
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goto fail_user_page;
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for (i = 0; i < nr_pages; i++) {
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rb->data_pages[i] = perf_mmap_alloc_page(cpu);
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if (!rb->data_pages[i])
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goto fail_data_pages;
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}
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rb->nr_pages = nr_pages;
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ring_buffer_init(rb, watermark, flags);
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return rb;
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fail_data_pages:
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for (i--; i >= 0; i--)
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free_page((unsigned long)rb->data_pages[i]);
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free_page((unsigned long)rb->user_page);
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fail_user_page:
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kfree(rb);
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fail:
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return NULL;
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}
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static void perf_mmap_free_page(unsigned long addr)
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{
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struct page *page = virt_to_page((void *)addr);
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page->mapping = NULL;
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__free_page(page);
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}
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void rb_free(struct ring_buffer *rb)
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{
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int i;
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perf_mmap_free_page((unsigned long)rb->user_page);
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for (i = 0; i < rb->nr_pages; i++)
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perf_mmap_free_page((unsigned long)rb->data_pages[i]);
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kfree(rb);
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}
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#else
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static int data_page_nr(struct ring_buffer *rb)
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{
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return rb->nr_pages << page_order(rb);
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}
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struct page *
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perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
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{
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/* The '>' counts in the user page. */
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if (pgoff > data_page_nr(rb))
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return NULL;
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return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
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}
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static void perf_mmap_unmark_page(void *addr)
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{
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struct page *page = vmalloc_to_page(addr);
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page->mapping = NULL;
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}
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static void rb_free_work(struct work_struct *work)
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{
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struct ring_buffer *rb;
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void *base;
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int i, nr;
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rb = container_of(work, struct ring_buffer, work);
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nr = data_page_nr(rb);
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base = rb->user_page;
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/* The '<=' counts in the user page. */
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for (i = 0; i <= nr; i++)
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perf_mmap_unmark_page(base + (i * PAGE_SIZE));
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vfree(base);
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kfree(rb);
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}
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void rb_free(struct ring_buffer *rb)
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{
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schedule_work(&rb->work);
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}
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struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
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{
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struct ring_buffer *rb;
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unsigned long size;
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void *all_buf;
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size = sizeof(struct ring_buffer);
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size += sizeof(void *);
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rb = kzalloc(size, GFP_KERNEL);
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if (!rb)
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goto fail;
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INIT_WORK(&rb->work, rb_free_work);
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all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
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if (!all_buf)
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goto fail_all_buf;
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rb->user_page = all_buf;
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rb->data_pages[0] = all_buf + PAGE_SIZE;
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rb->page_order = ilog2(nr_pages);
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rb->nr_pages = !!nr_pages;
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ring_buffer_init(rb, watermark, flags);
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return rb;
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fail_all_buf:
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kfree(rb);
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fail:
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return NULL;
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}
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#endif
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