On 2015-01-28 10:35:28 -0500, Tom Lane wrote: > Andres Freund <and...@2ndquadrant.com> writes: > > On 2015-01-26 21:13:31 -0500, Robert Haas wrote: > >> So maybe we should also do something like what LWLocks do, and make a > >> union between the actual structure and an appropriate array of padding > >> bytes - say either 64 or 128 of them. > > > Hm. That's a bit bigger patch. I'm inclined to just let it slide for the > > moment. I still have plans to downsize some of sbufdesc's content (move > > the io lock out) and move the content lwlock inline. Then we're not > > going to have much choice but do this... > > Even if you didn't have plans like that, it would be entire folly to > imagine that buffer headers will be exactly 64 bytes without some forcing > function for that.
Meh. The 128 byte additionally used by the alignment don't hurt in any case. But forcing all buffer descriptors to 64bit on a 32bit platform isn't guaranteed to be performance neutral. So, no I don't think it's a "folly" to do so. I'd rather make actual progress that improves the absurd situation today (a factor of 2-3 by changing max_connections by one...) than argue whether the impact on 32bit platforms is acceptable before doing so. If we additionally decide to pad the struct, fine. But I don't see why this has to be done at the same time. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers