Re: strict aliasing

Robert Haas <robertmhaas@gmail.com> wrote:
> Kevin Grittner <Kevin.Grittner@wicourts.gov> wrote:
 
>> This suggests that in the long term, it might be worth [...]
 
> The other possibility is that the OS is smart enough about moving
> things around to get good locality that sticking locality hints on
> top doesn't really make any difference.  Certainly, I would expect
> any OS to be smart enough to allocate backend-local memory on the
> same processor where the task is running, and to avoid moving
> processes between cells more than necessary.
 
Right.  I'm not sure that it will make any more sense to do this
than to do raw access to a disk partition.  I don't think it's a
given that we can do a better job of this than the OS does.
 
> Regarding results instability [...] My working theory is that this
> is the result of spinlock contention.
 
> So my theory is that now the performance goes down more or less
> "permanently", unless or until there's some momentary break in the
> action that lets the queue of people waiting for that spinlock
> drain out.  This is just a wild-ass guess, and I might be totally
> wrong...
 
Well, I suspect that you're basing that guess on enough evidence
that it's more likely to be right than the wild-assed guesses I've
been throwing out there.  :-)  I can't say it's inconsistent with
anything I've seen.
 
-Kevin