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authorEric Dumazet <dada1@cosmosbay.com>2008-11-23 23:24:32 -0800
committerDavid S. Miller <davem@davemloft.net>2008-11-23 23:24:32 -0800
commit1f87e235e6fb92c2968b52b9191de04f1aff8e77 (patch)
treeab774d239c61b6c206ef07398828533cdd01915e /mm/tiny-shmem.c
parent70eb1bfd52e97120eddf9b5aaabfe1ecdf4eb663 (diff)
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eth: Declare an optimized compare_ether_addr_64bits() function
Linus mentioned we could try to perform long word operations, even on potentially unaligned addresses, on x86 at least. David mentioned the HAVE_EFFICIENT_UNALIGNED_ACCESS test to handle this on all arches that have efficient unailgned accesses. I tried this idea and got nice assembly on 32 bits: 158: 33 82 38 01 00 00 xor 0x138(%edx),%eax 15e: 33 8a 34 01 00 00 xor 0x134(%edx),%ecx 164: c1 e0 10 shl $0x10,%eax 167: 09 c1 or %eax,%ecx 169: 74 0b je 176 <eth_type_trans+0x87> And very nice assembly on 64 bits of course (one xor, one shl) Nice oprofile improvement in eth_type_trans(), 0.17 % instead of 0.41 %, expected since we remove 8 instructions on a fast path. This patch implements a compare_ether_addr_64bits() function, that uses the CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS ifdef to efficiently perform the 6 bytes comparison on all capable arches. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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