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authorHannes Frederic Sowa <hannes@stressinduktion.org>2014-11-05 00:23:04 +0100
committerDavid S. Miller <davem@davemloft.net>2014-11-05 22:01:21 -0500
commite5a2c899957659cd1a9f789bc462f9c0b35f5150 (patch)
tree4c9b8a6f89d961daf9ada9f5ee95f8b371ce3a04 /include/linux/hash.h
parent2c99cd914d4fed9160d98849c9dd38034616768e (diff)
fast_hash: avoid indirect function calls
By default the arch_fast_hash hashing function pointers are initialized to jhash(2). If during boot-up a CPU with SSE4.2 is detected they get updated to the CRC32 ones. This dispatching scheme incurs a function pointer lookup and indirect call for every hashing operation. rhashtable as a user of arch_fast_hash e.g. stores pointers to hashing functions in its structure, too, causing two indirect branches per hashing operation. Using alternative_call we can get away with one of those indirect branches. Acked-by: Daniel Borkmann <dborkman@redhat.com> Cc: Thomas Graf <tgraf@suug.ch> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/hash.h')
-rw-r--r--include/linux/hash.h34
1 files changed, 0 insertions, 34 deletions
diff --git a/include/linux/hash.h b/include/linux/hash.h
index d0494c399392..6e8fb028848c 100644
--- a/include/linux/hash.h
+++ b/include/linux/hash.h
@@ -84,38 +84,4 @@ static inline u32 hash32_ptr(const void *ptr)
return (u32)val;
}
-struct fast_hash_ops {
- u32 (*hash)(const void *data, u32 len, u32 seed);
- u32 (*hash2)(const u32 *data, u32 len, u32 seed);
-};
-
-/**
- * arch_fast_hash - Caclulates a hash over a given buffer that can have
- * arbitrary size. This function will eventually use an
- * architecture-optimized hashing implementation if
- * available, and trades off distribution for speed.
- *
- * @data: buffer to hash
- * @len: length of buffer in bytes
- * @seed: start seed
- *
- * Returns 32bit hash.
- */
-extern u32 arch_fast_hash(const void *data, u32 len, u32 seed);
-
-/**
- * arch_fast_hash2 - Caclulates a hash over a given buffer that has a
- * size that is of a multiple of 32bit words. This
- * function will eventually use an architecture-
- * optimized hashing implementation if available,
- * and trades off distribution for speed.
- *
- * @data: buffer to hash (must be 32bit padded)
- * @len: number of 32bit words
- * @seed: start seed
- *
- * Returns 32bit hash.
- */
-extern u32 arch_fast_hash2(const u32 *data, u32 len, u32 seed);
-
#endif /* _LINUX_HASH_H */