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| author | Peter Zijlstra <peterz@infradead.org> | 2013-10-31 17:36:25 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2013-11-06 12:34:22 +0100 |
| commit | 524feca5e9da9e5f9e5aa5d5613b1d762db9509e (patch) | |
| tree | 12052071d8db98961cc9114a183d4ee1752db0a9 /kernel/events | |
| parent | d20a973f46ed83e0d7d24f6c512064133038e193 (diff) | |
| download | linux-524feca5e9da9e5f9e5aa5d5613b1d762db9509e.tar.gz linux-524feca5e9da9e5f9e5aa5d5613b1d762db9509e.tar.bz2 linux-524feca5e9da9e5f9e5aa5d5613b1d762db9509e.zip | |
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>
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/ring_buffer.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index e4d70f33792f..c52a32fa5592 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; |