On Saturday, December 24, 2011 05:01:02 PM Simon Riggs wrote: > On Sat, Dec 24, 2011 at 3:54 PM, Andres Freund <and...@anarazel.de> wrote: > > On Saturday, December 24, 2011 03:46:16 PM Tom Lane wrote: > >> Simon Riggs <si...@2ndquadrant.com> writes: > >> > After the various recent discussions on list, I present what I believe > >> > to be a working patch implementing 16-but checksums on all buffer > >> > pages. > >> > >> I think locking around hint-bit-setting is likely to be unworkable from > >> a performance standpoint. I also wonder whether it might not result in > >> deadlocks. > > > > Why don't you use the same tricks as the former patch and copy the > > buffer, compute the checksum on that, and then write out that copy (you > > can even do both at the same time). I have a hard time believing that > > the additional copy is more expensive than the locking. > > We would copy every time we write, yet lock only every time we set hint > bits. Isn't setting hint bits also a rather frequent operation? At least in a well- cached workload where most writeout happens due to checkpoints.
> If that option is favoured, I'll write another version after Christmas. Seems less complicated (wrt deadlocking et al) to me. But I havent read your patch, so I will shut up now ;) Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
