On Wed, Feb 5, 2014 at 11:37 AM, Andres Freund <and...@2ndquadrant.com> wrote: > 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.
I thought your previous idea of increasing BUFFERALIGN to 64 bytes had a lot to recommend it. But that doesn't mean it doesn't need testing. -- 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
