Re: [HACKERS] fork/exec for backend

>
>
> On 24 Jan 1998, Goran Thyni wrote:
>
> > Fork on modern unices (linux and (a think) *BSD) cost
> > almost nothing (in time and memory) thanks to COW (copy-on-write).
> > Exec in expensive as it breaks COW.
>
> Not so. Modern Unixs will share executable address space between
> processes. So if you fork and exec 10 identical programs, they will share
> most address space.
>
> If you want to speed this up, link postgresql static. This makes exec()
> cost almost nothing too. postgresql becomes its own best shared library.
>
> Again, this only applies to "modern" systems, but FreeBSD definitely has
> this behaviour.

This is very OS-specific. SunOS-style shared libraries do have a
noticable overhead for each function call. In fact, even though these
are part of BSD44 source, BSDI does not use them, and uses a more crude
shared library jump table, similar to SVr3 shared libraries because of
the SunOS shared library overhead.

I think FreeBSD and Lunix use SunOS style shared libraries, often called
dynamic shared libraries because you can change the function while the
binary is running if you are realy careful.

--
Bruce Momjian
maillist(at)candle(dot)pha(dot)pa(dot)us