On Sat, Mar 23, 2013 at 3:10 PM, Andres Freund <and...@2ndquadrant.com> wrote: >> Andres showed that switching out the existing CRC for zlib's would >> result in 8-30% increase in INSERT-SELECT speed >> (http://www.postgresql.org/message-id/201005202227.49990.and...@anarazel.de) >> with the speeded up CRC still showing up as 10% of the profile. So I >> guess another 5% speedup by doing the CRC 8 bytes at a time instead of >> the used 4. And another couple % by using Fletcher or SIMD. > > I am not sure the considerations for WAL are the same as for page checksums - > the current WAL code only computes the CRCs in rather small chunks, so very > pipelineable algorithms/implementations don't necessarly show the same benefit > for WAL as they do for page checksums...
Sure, but I think that WAL checksums are not a big overhead in that case anyway. I should point out that getting the SIMD algorithm to not be a loss for small variable sized workloads will take considerable amount of effort and code. Whereas it's quite easy for pipelined CRC32 and Fletcher (or should I say Adler as we want to use mod 65521). 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
