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Date:      Mon, 07 Aug 2000 15:14:56 -0700
From:      David Greenman <dg@root.com>
To:        Paul Richards <paul@originative.co.uk>
Cc:        Poul-Henning Kamp <phk@critter.freebsd.dk>, Alfred Perlstein <bright@wintelcom.net>, Matt Dillon <dillon@earth.backplane.com>, Mike Smith <msmith@FreeBSD.ORG>, Stephen McKay <mckay@thehub.com.au>, freebsd-current@FreeBSD.ORG, dillon@FreeBSD.ORG
Subject:   Re: Ugly, slow shutdown 
Message-ID:  <200008072214.PAA04340@implode.root.com>
In-Reply-To: Your message of "Mon, 07 Aug 2000 23:21:48 BST." <398F367C.27DD39DA@originative.co.uk> 

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>I did say "as a general rule". If you know that "by design" nothing else
>is going to mess with what you're sleeping on before you wake up then
>you can make tighter optimisations but that's not the general case.
>There is such a thing as over optimisation though and for the sake of a
>simple if statement it is probably better to write code that is robust
>to changes made elsewhere in the system rather than squeeze every inch
>of performance out of the code, unless there's a real need to optimize
>in that particular area.

   In some cases it isn't practical or very expensive to verify that the
condition that caused the sleep in the first place has been satisfied - that's
often why certain parts of the kernel rely on the established tsleep symantics.

-DG

David Greenman
Co-founder, The FreeBSD Project - http://www.freebsd.org
Manufacturer of high-performance Internet servers - http://www.terasolutions.com
Pave the road of life with opportunities.


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