Date: Wed, 24 May 2000 20:28:00 -0600 From: Chuck Paterson <cp@bsdi.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Terry Lambert <tlambert@primenet.com>, arch@freebsd.org Subject: Re: Preemptive kernel on older X86 hardware Message-ID: <200005250228.UAA16415@berserker.bsdi.com>
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We are seeing 30 clock ticks for a locked mutex
operation. Only 10 if you take out the lock for UP
systems. (hopefully I did the math right.) I just don't see how
putting a function call is going to be cheap relatively.
Is it possible that you are hitting so many
spin locks that the function calltime gets burried.
Chuck
----- Begin Included Message -----
Date: Wed, 24 May 2000 19:08:00 -0700
From: Matthew Dillon <dillon@apollo.backplane.com>
To: Chuck Paterson <cp@bsdi.com>
Subject: Re: Preemptive kernel on older X86 hardware
cc: Terry Lambert <tlambert@primenet.com>, arch@FreeBSD.ORG
We've had very good luck encapsulating our MP lock code in real
honest-to-god subroutines rather then trying to make them inline
macros.
On intel anyway, subroutine calls are *cheap*, especially compared
to the overhead of a locked instruction or even an L1 cache miss.
It's a no-brainer.
-Matt
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