diff options
author | Peter Zijlstra <peterz@infradead.org> | 2013-10-31 10:19:59 +0100 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2013-11-06 12:34:18 +0100 |
commit | 26c86da8821f7b64fced498674990318bc34c8de (patch) | |
tree | 140d2b7c5f0e6e5afd106d3e76793d2be64e8592 /kernel/events/ring_buffer.c | |
parent | 83bf9702c876a54e4e4d1735f9c8680a72421fbe (diff) | |
download | op-kernel-dev-26c86da8821f7b64fced498674990318bc34c8de.zip op-kernel-dev-26c86da8821f7b64fced498674990318bc34c8de.tar.gz |
perf: Simplify the ring-buffer code
By using CIRC_SPACE() we can obviate the need for perf_output_space().
Shrinks the size of perf_output_begin() by 17 bytes on
x86_64-defconfig.
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-vtb0xb0llebmsdlfn1v5vtfj@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events/ring_buffer.c')
-rw-r--r-- | kernel/events/ring_buffer.c | 37 |
1 files changed, 4 insertions, 33 deletions
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 9c2ddfb..6929c58 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -12,40 +12,10 @@ #include <linux/perf_event.h> #include <linux/vmalloc.h> #include <linux/slab.h> +#include <linux/circ_buf.h> #include "internal.h" -static bool perf_output_space(struct ring_buffer *rb, unsigned long tail, - unsigned long offset, unsigned long head) -{ - unsigned long sz = perf_data_size(rb); - unsigned long mask = sz - 1; - - /* - * check if user-writable - * overwrite : over-write its own tail - * !overwrite: buffer possibly drops events. - */ - if (rb->overwrite) - return true; - - /* - * verify that payload is not bigger than buffer - * otherwise masking logic may fail to detect - * the "not enough space" condition - */ - if ((head - offset) > sz) - return false; - - 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); @@ -181,9 +151,10 @@ int perf_output_begin(struct perf_output_handle *handle, tail = ACCESS_ONCE(rb->user_page->data_tail); smp_mb(); offset = head = local_read(&rb->head); - head += size; - if (unlikely(!perf_output_space(rb, tail, offset, head))) + if (!rb->overwrite && + unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size)) goto fail; + head += size; } while (local_cmpxchg(&rb->head, offset, head) != offset); if (head - local_read(&rb->wakeup) > rb->watermark) |