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From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no>
To: John Baldwin <jhb@freebsd.org>
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	<201206051008.29568.jhb@freebsd.org> <86haupvk4a.fsf@ds4.des.no>
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Date: Tue, 05 Jun 2012 19:40:13 +0200
In-Reply-To: <201206051222.12627.jhb@freebsd.org> (John Baldwin's message of
	"Tue, 5 Jun 2012 12:22:12 -0400")
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Cc: Gianni <gianni@freebsd.org>, Alan Cox <alc@rice.edu>,
	Alexander Kabaev <kan@freebsd.org>, Attilio Rao <attilio@freebsd.org>,
	Konstantin Belousov <kib@freebsd.org>, freebsd-arch@freebsd.org,
	Konstantin Belousov <kostikbel@gmail.com>
Subject: Re: Fwd: [RFC] Kernel shared variables
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John Baldwin <jhb@freebsd.org> writes:
> Yes, we know getpid() is slow, I think the question is does it matter tha=
t=20
> it's slow in something other than a microbenchmark.  Can you name the=20
> application that you've seen use getpid()?

I've seen it in a proprietary multi-platform shared memory library.

Closer to home, I believe sqlite3 does the same thing, and we do this
ourselves, albeit on a smaller, non-performance-critical scale, e.g. in
the pidfile API and (IIRC) in nsswitch and the resolver.

BTW, raise(0) was a poor choice of baseline since it actually calls
getpid(), which makes no difference on Linux but does on FreeBSD.  The
actual numbers for FreeBSD are:

getpid(): 10,000,000 iterations in 784,638 ms
gettimeofday(0, 0): 10,000,000 iterations in 801,375 ms
kill(pid, 0): 10,000,000 iterations in 1,190,791 ms

DES
--=20
Dag-Erling Sm=C3=B8rgrav - des@des.no