The basis of hash_words64() was 64 bits, even when the hash value is
32 bits, thus confusing the domain and the range of the function.
This patch fixes this by making the basis an uint32_t.
Suggested-by: Ben Pfaff <blp@nicira.com>
Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Use CRC32 intrinsics for hash computations when building for
X86_64 with SSE4_2.
Add a new hash_words64() and change hash_words() to be inlined when
'n_words' is a compile-time constant.
Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
Use generic names hash_add() and hash_finish() instead of mhash_*
equivalents. This makes future changes to hash implentations more
localized.
Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
This commit fixes the warning issued by 'clang' when pointer is casted
to one with greater alignment.
Signed-off-by: Alex Wang <alexw@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
murmurhash is faster than Jenkins and slightly higher quality, so switch to
it for hashing words.
The best timings I got for hashing for data lengths of the following
numbers of 32-bit words, in seconds per 1,000,000,000 hashes, were:
words murmurhash Jenkins hash
----- ---------- ------------
1 8.4 10.4
2 10.3 10.3
3 11.2 10.7
4 12.6 18.0
5 13.9 18.3
6 15.2 18.7
In other words, murmurhash outperforms Jenkins for all input lengths other
than exactly 3 32-bit words (12 bytes). (It's understandable that Jenkins
would have a best case at 12 bytes, because Jenkins works in 12-byte
chunks.) Even in the case where Jenkins is faster, it's only by 5%. On
average within this data set, murmurhash is 15% faster, and for 4-word
input it is 30% faster.
We retain Jenkins for flow_hash_symmetric_l4() and flow_hash_fields(),
which are cases where the hash value is exposed externally.
This commit appears to improve "ovs-benchmark rate" results slightly by
a few hundred connections per second (under 1%), when used with an NVP
controller.
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Ethan Jackson <ethan@nicira.com>
murmurhash includes an xor with the number of bytes hashed in its finishing
step. Until now, we've only had murmurhash for full words, but an upcoming
commit adds murmurhash for bytes, so the finishing function will need to
take a count of bytes instead.
Signed-off-by: Ben Pfaff <blp@nicira.com>
Murmurhash is generally superior to the Jenkins lookup3 hash according to
the available figures. Perhaps we should generally replace our current
hashes by murmurhash.
For now, I'm introducing a parallel implementation to allow it to be used
in cases where an incremental one-word-at-a-time hash is desirable. The
first user will be added in an upcoming commit.
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Ethan Jackson <ethan@nicira.com>
Replaced all instances of Nicira Networks(, Inc) to Nicira, Inc.
Feature #10593
Signed-off-by: Raju Subramanian <rsubramanian@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
I always assumed that macros would generate better code. I was wrong. The
generated code was identical with inline functions, with GCC version 4.4.5.
Signed-off-by: Ben Pfaff <blp@nicira.com>
It's easier for the client to pass in data directly than it is for the
client to stuff it into an array.
These functions will have new users in upcoming commits.
