Messages in this thread Patch in this message | | | Date | Wed, 6 Nov 2013 05:19:05 -0800 | From | tip-bot for Peter Zijlstra <> | Subject | [tip:perf/core] perf: Optimize perf_output_begin() -- address calculation |
| |
Commit-ID: 524feca5e9da9e5f9e5aa5d5613b1d762db9509e Gitweb: http://git.kernel.org/tip/524feca5e9da9e5f9e5aa5d5613b1d762db9509e Author: Peter Zijlstra <peterz@infradead.org> AuthorDate: Thu, 31 Oct 2013 17:36:25 +0100 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 6 Nov 2013 12:34:22 +0100
perf: Optimize perf_output_begin() -- address calculation
Rewrite the handle address calculation code to be clearer.
Saves 8 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-3trb2n2henb9m27tncef3ag7@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org> --- kernel/events/ring_buffer.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index e4d70f3..c52a32f 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -105,7 +105,7 @@ int perf_output_begin(struct perf_output_handle *handle, { struct ring_buffer *rb; unsigned long tail, offset, head; - int have_lost; + int have_lost, page_shift; struct { struct perf_event_header header; u64 id; @@ -159,12 +159,12 @@ int perf_output_begin(struct perf_output_handle *handle, if (unlikely(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; + page_shift = PAGE_SHIFT + page_order(rb); + + handle->page = (offset >> page_shift) & (rb->nr_pages - 1); + offset &= (1UL << page_shift) - 1; + handle->addr = rb->data_pages[handle->page] + offset; + handle->size = (1UL << page_shift) - offset; if (unlikely(have_lost)) { struct perf_sample_data sample_data;
| |