Robert Haas <robertmh...@gmail.com> writes: > On Mon, Aug 29, 2011 at 11:07 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> Robert Haas <robertmh...@gmail.com> writes: >>> IIUC, this is basically total nonsense.
>> It could maybe be rewritten for more clarity, but it's far from being >> nonsense. The responsibility for having an actual hardware memory fence >> instruction lies with the author of the TAS macro. > Right... but the comment implies that you probably don't need one, and > doesn't even mention that you MIGHT need one. I think maybe we need to split it into two paragraphs, one addressing the TAS author and the other for the TAS user. I'll have a go at that. > I think optimizing spinlocks for machines with only a few CPUs is > probably pointless. Based on what I've seen so far, spinlock > contention even at 16 CPUs is negligible pretty much no matter what > you do. We did find significant differences several years ago, testing on machines that probably had no more than four cores; that's where the existing comments in s_lock.h came from. Whether those tests are still relevant for today's source code is not obvious though. 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