On 2014-02-05 11:23:29 -0500, Tom Lane wrote: > Andres Freund <and...@2ndquadrant.com> writes: > > And I think somebody already thought about it (c.f. ALIGNOF_BUFFER), it > > just wasn't updated in the last 10 years. > > No, ALIGNOF_BUFFER is there because we read something that said that I/O > transfers between userspace and kernel disk cache would be faster with > aligned buffers. There's been no particular thought given to alignment > of other data structures, AFAIR.
But it's not aligned anymore on at last half a decade's hardware, and it's what we already align *all* bigger ShmemAlloc() values with. And BufferDescriptors surely counts as larger in its entirety. > It may well be that your proposal is spot on. But I'd like to see some > data-structure-by-data-structure measurements, rather than assuming that > alignment must be a good thing. I am fine with just aligning BufferDescriptors properly. That has clearly shown massive improvements. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
