That's not entirely true. CRC-32C beats pretty much everything with the same length quality-wise and has both hardware implementations and highly optimized software versions. Em 12/09/2014 17:18, "Ants Aasma" <a...@cybertec.at> escreveu:
> 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 > -- > Cybertec Schönig & Schönig GmbH > Gröhrmühlgasse 26 > A-2700 Wiener Neustadt > Web: http://www.postgresql-support.de > > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers >
