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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: 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>
This commit is contained in:
Peter Zijlstra 2013-10-31 17:36:25 +01:00 committed by Ingo Molnar
parent d20a973f46
commit 524feca5e9
1 changed files with 7 additions and 7 deletions
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14
kernel/events/ring_buffer.c
View File

@ -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;