2011/5/15 Robert Haas <robertmh...@gmail.com>: > On Fri, May 6, 2011 at 5:31 PM, Greg Smith <g...@2ndquadrant.com> wrote: >> I think that all the complexity with CRCs etc. is unlikely to lead anywhere >> too, and those two issues are not completely unrelated. The simplest, >> safest thing here is the right way to approach this, not the most >> complicated one, and a simpler format might add some flexibility here to >> reload more cache state too. The bottleneck on reloading the cache state is >> reading everything from disk. Trying to micro-optimize any other part of >> that is moving in the wrong direction to me. I doubt you'll ever measure a >> useful benefit that overcomes the expense of maintaining the code. And you >> seem to be moving to where someone can't restore cache state when they >> change shared_buffers. A simpler implementation might still work in that >> situation; reload until you run out of buffers if shared_buffers shrinks, >> reload until you're done with the original size. > > I don't think there's any need for this to get data into > shared_buffers at all. Getting it into the OS cache oughta be plenty > sufficient, no? > > ISTM that a very simple approach here would be to save the contents of > each shared buffer on clean shutdown, and to POSIX_FADV_WILLNEED those > buffers on startup.
+1 It is just an evolution of the current process if I understood the explantions of the latest patch correctly. >We could worry about additional complexity, like > using fincore to probe the OS cache, in a follow-on patch. While > reloading only 8GB of maybe 30GB of cached data on restart would not > be as good as reloading all of it, it would be a lot better than > reloading none of it, and the gymnastics required seems substantially > less. > > -- > Robert Haas > EnterpriseDB: http://www.enterprisedb.com > The Enterprise PostgreSQL Company > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers > -- Cédric Villemain 2ndQuadrant http://2ndQuadrant.fr/ PostgreSQL : Expertise, Formation et Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers