Date: Thu, 15 Apr 1999 15:19:45 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: current@FreeBSD.ORG Subject: Re: RE: swap-related problems Message-ID: <199904152219.PAA48993@apollo.backplane.com> References: <Pine.BSF.3.96.990414035810.4169g-100000@cygnus.rush.net>
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Just a quick note... I've heard 'vfork' and 'fork' mentioned twice now.
I think there is some confusion. fork() does not really eat that
much memory if all you are doing is fork/exec. The only difference
between fork and vfork from a resource point of view is around 32 KBytes
of memory and a little extra cpu, and even the memory is recovered
when you do the exec.
Semantically, they are quite different - vfork is supposed to share
the parent process's address space until it exec's whereas fork does not.
But FreeBSD's updated VM model, which you can thank John Dyson for mostly,
is extremely efficient even when forking whole address spaces.
The differences between fork and vfork are also irrelevant in this
particular discussion since the fork/exec combination is only in
the 'fork' state for a very short time. The moment you exec, the
address space is wiped ( except for mmap's MAP_INHERIT, which very few
people ever use ).
-Matt
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