On Fri, Sep 12, 2014 at 11:17:12PM +0300, Ants Aasma wrote: > On Fri, Sep 12, 2014 at 10:38 PM, Heikki Linnakangas > <hlinnakan...@vmware.com> wrote: > > I don't mean that we should abandon this patch - compression makes the WAL > > smaller which has all kinds of other benefits, even if it makes the raw TPS > > throughput of the system worse. But I'm just saying that these TPS > > comparisons should be taken with a grain of salt. We probably should > > consider switching to a faster CRC algorithm again, regardless of what we do > > with compression. > > CRC is a pretty awfully slow algorithm for checksums. We should > consider switching it out for something more modern. CityHash, > MurmurHash3 and xxhash look like pretty good candidates, being around > an order of magnitude faster than CRC. I'm hoping to investigate > substituting the WAL checksum algorithm 9.5. > > Given the room for improvement in this area I think it would make > sense to just short-circuit the CRC calculations for testing this > patch to see if the performance improvement is due to less data being > checksummed. > > Regards, > Ants Aasma
+1 for xxhash - version speed on 64-bits speed on 32-bits ------- ---------------- ---------------- XXH64 13.8 GB/s 1.9 GB/s XXH32 6.8 GB/s 6.0 GB/s Here is a blog about its performance as a hash function: http://fastcompression.blogspot.com/2014/07/xxhash-wider-64-bits.html Regards, Ken -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers