On Sat, Jan 21, 2017 at 09:02:25PM +0200, Ants Aasma wrote: > > It might be worth looking into using the CRC CPU instruction to reduce this > > overhead, like we do for the WAL checksums. Since that is a different > > algorithm it would be a compatibility break and we would need to support the > > old algorithm for upgraded clusters.. > > We looked at that when picking the algorithm. At that point it seemed > that CRC CPU instructions were not universal enough to rely on them. > The algorithm we ended up on was designed to be fast on SIMD hardware. > Unfortunately on x86-64 that required SSE4.1 integer instructions, so > with default compiles there is a lot of performance left on table. A > low hanging fruit would be to do CPU detection like the CRC case and > enable a SSE4.1 optimized variant when those instructions are > available. IIRC it was actually a lot faster than the naive hardware > CRC that is used for WAL and about on par with interleaved CRC.
Uh, I thought already did compile-time testing for SSE4.1 and used them if present. Why do you say "with default compiles there is a lot of performance left on table?" -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + As you are, so once was I. As I am, so you will be. + + Ancient Roman grave inscription + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
