From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <dff955d24d071515581495be905b665d@quanstro.net>
From: erik quanstrom <quanstro@quanstro.net>
Date: Tue, 24 Feb 2009 10:54:43 -0500
To: ben@flyingwalrus.net, 9fans@9fans.net
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Subject: Re: [9fans] Calling vac from C
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> about 5 years ago i took a class on performance tuning Solaris.
>
> The instructor claimed that fork was expensive because accounting is never really turned off, just piped to /dev/null.  there is no accounting overhead for threads.
>
> I never bothered to verify this, but now that this comes up, I'd tempted.

there's no need to guess.  here's the source code.

http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/os/fork.c

cfork is ~525 lines long and seems to take the curious tack of
forking all the lwps associated with a process.  i don't
see any accounting, but i see at least 9 + nlwp + nresourcectls
mutex locks if you follow the regular fork path.  what is the
accounting that you're thinking of?  it would be easy to miss.

- erik