Commit-ID: 26c86da8821f7b64fced498674990318bc34c8de Gitweb: http://git.kernel.org/tip/26c86da8821f7b64fced498674990318bc34c8de Author: Peter Zijlstra <pet...@infradead.org> AuthorDate: Thu, 31 Oct 2013 10:19:59 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Wed, 6 Nov 2013 12:34:18 +0100
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 <pet...@infradead.org> Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org> Cc: Frederic Weisbecker <fweis...@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoy...@polymtl.ca> Cc: Michael Ellerman <mich...@ellerman.id.au> Cc: Michael Neuling <mi...@neuling.org> Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> Cc: james.ho...@imgtec.com Cc: Vince Weaver <vi...@deater.net> Cc: Victor Kaplansky <vict...@il.ibm.com> Cc: Oleg Nesterov <o...@redhat.com> Cc: Anton Blanchard <an...@samba.org> Link: http://lkml.kernel.org/n/tip-vtb0xb0llebmsdlfn1v5v...@git.kernel.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/events/ring_buffer.c | 37 ++++--------------------------------- 1 file 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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
