Robert Haas <robertmhaas@gmail.com> writes:
> On Sat, Nov 27, 2010 at 11:18 PM, Bruce Momjian <bruce@momjian.us> wrote:
>> Not sure that information moves us forward. �If the postmaster cleared
>> the memory, we would have COW in the child and probably be even slower.
> Well, we can determine the answers to these questions empirically.
Not really. Per Bruce's description, a page would become COW the moment
the postmaster touched (either write or read) any variable on it. Since
we have no control over how the loader lays out static variables, the
actual behavior of a particular build would be pretty random and subject
to unexpected changes caused by seemingly unrelated edits.
Also, the referenced URL only purports to describe the behavior of
HPUX, which is not exactly a mainstream OS. I think it requires a
considerable leap of faith to assume that all or even most platforms
work the way this suggests, and not in the dumber fashion Andres
suggested. Has anybody here actually looked at the relevant Linux
or BSD kernel code?
regards, tom lane