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Commit 524feca5 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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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: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent d20a973f

kernel/events/ring_buffer.c

+7 −7
Original line number Diff line number Diff line
@@ -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;