Re: performance tuning: shared_buffers, sort_mem; swap - Mailing list pgsql-admin

David Gilbert <dgilbert@velocet.ca> writes:
> "Tom" == Tom Lane <tgl@sss.pgh.pa.us> writes:
> Tom> Well, I must say this is the first time I've heard of "BSD-style
> Tom> shared memory".

> The canonical example is to mmap() a file multiply.

Oh.  Yes, as Curt said, this issue has been beaten to death already;
see the archives.

You could in fact use a MAP_ANON region as a replacement for SysV shared
memory, but AFAICT you would lose a rather important interlock against
starting a new postmaster when old backends remain alive.  Ugly as the
SysV API is, it does some things we need rather nicely.

> One bonus of bsd shared memory (when anonymous) is that it dies with
> the process ... even in the worst case.

But in fact we don't *want* it to be anonymous.

            regards, tom lane