Greg Stark <gsst...@mit.edu> writes: > On Mon, Nov 29, 2010 at 12:12 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> Really you do want to scrape the value.
> Couldn't we just round the shared memory allocation down to a multiple > of 4MB? That would handle all older architectures where the size is > 2MB or 4MB. Rounding *down* will not work, at least not without extremely invasive changes to the shmem allocation code. Rounding up is okay, as long as you don't mind some possibly-wasted space. > I see online that IA64 supports larger page sizes up to 256MB but then > could we make it the user's problem if they change their hugepagesize > to a larger value to pick a value of shared_buffers that will fit > cleanly? We might need to rejigger things so that the shared memory > segment is exactly the size of shared_buffers and any other shared > data structures are in a separate segment though for that to work. Two shmem segments would be a pretty serious PITA too, certainly a lot more so than a few lines to read a magic number from /proc. But this is all premature pending a demonstration that there's enough potential gain here to be worth taking any trouble at all. The one set of numbers we have says otherwise. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers