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| /openbmc/linux/arch/powerpc/include/asm/ |
| H A D | page_64.h | diff e35735b9a5d8d38d9ffe2f1f0cdcbb0d45c42eff Thu Oct 02 00:44:21 CDT 2014 Anton Blanchard <anton@samba.org> powerpc: Speed up clear_page by unrolling it
Unroll clear_page 8 times. A simple microbenchmark which
allocates and frees a zeroed page:
for (i = 0; i < iterations; i++) {
unsigned long p = __get_free_page(GFP_KERNEL | __GFP_ZERO);
free_page(p);
}
improves 20% on POWER8.
This assumes cacheline sizes won't grow beyond 512 bytes or
page sizes wont drop below 1kB, which is unlikely, but we could
add a runtime check during early init if it makes people nervous.
Michael found that some versions of gcc produce quite bad code
(all multiplies), so we give gcc a hand by using shifts and adds.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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