Commit-ID: 524feca5e9da9e5f9e5aa5d5613b1d762db9509e Gitweb: http://git.kernel.org/tip/524feca5e9da9e5f9e5aa5d5613b1d762db9509e Author: Peter Zijlstra <[email protected]> AuthorDate: Thu, 31 Oct 2013 17:36:25 +0100 Committer: Ingo Molnar <[email protected]> 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 <[email protected]> Cc: Benjamin Herrenschmidt <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Mathieu Desnoyers <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Michael Neuling <[email protected]> Cc: "Paul E. McKenney" <[email protected]> Cc: [email protected] Cc: Vince Weaver <[email protected]> Cc: Victor Kaplansky <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Anton Blanchard <[email protected]> Link: http://lkml.kernel.org/n/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
