On 18 September 2014 11:03, Ben Pfaff <b...@nicira.com> wrote: > On Mon, Sep 15, 2014 at 02:25:13PM +1200, Joe Stringer wrote: > > Add the 128-bit murmurhash by Austin Appleby, for 32-bit systems from: > > http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp > > > > Signed-off-by: Joe Stringer <joestrin...@nicira.com> > > Why does the loop in hash_words128 count up from a negative number to > zero? > > Please put spaces after commas and around binary infix operators, > e.g. in these cases: > k1 = hash_rot(k1,15); > hash.h[0] = hash_rot(hash.h[0],19); > hash.h[0] = hash.h[0]*5+0x561ccd1b; > and similar. >
Style changes from the original to OVS that I didn't pick up on. I can change these. > > It looks like there is a version of 128-bit murmurhash that uses 64-bit > operations. Did you consider it? Do you have any idea whether there is > a performance difference? > I didn't try that. I did try the 64-bit CityHash (64-bit operations) which is based on MurmurHash and is meant to have higher performance, and I couldn't determine much change. That said, I was testing revalidation as a whole and not the individual hash functions. > > Did you look at the GCC-generated code to see that it was sane? > No. Do you have particular things that you look for? Are you concerned about the ovs_u128 structure and whether access into/out of that is sensible? > Did you do any testing of the hash function output? We have tests for > our main hash function. > I can look into this. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
