From owner-freebsd-arch  Sun Feb 17 23:37:27 2002
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Date: Sun, 17 Feb 2002 23:36:58 -0800
From: Terry Lambert <tlambert2@mindspring.com>
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To: Matthew Dillon <dillon@apollo.backplane.com>
Cc: Bruce Evans <bde@zeta.org.au>,
	Poul-Henning Kamp <phk@critter.freebsd.dk>,
	Julian Elischer <julian@elischer.org>,
	Alfred Perlstein <bright@mu.org>, arch@FreeBSD.ORG, jhb@FreeBSD.ORG,
	peter@wemm.org, jake@locore.ca
Subject: Re: gettimeofday() and crhold()/crfree() (was Re:  
 gettimeofday()andcopyout().Is copyout() MPSAFE on non-i386 archs? )
References: <20020218151249.E4728-100000@gamplex.bde.org> <3C70AB8B.96589869@mindspring.com> <200202180733.g1I7Xej12207@apollo.backplane.com>
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Matthew Dillon wrote:
> :.4nsec * 22,000 transactions/sec * 5 timestamps/transaction
> := 440us/sec spent on time stamps.
> :
> :Up that to 2uS and... = 220ms/sec on time stamps = ~1/4 of
> :all available time spent on time stamps.
> :
> :[ ... other stuff not really applicable; can discuss why
> :      off list, if necessary ... ]
> 
>     This is a meaningless exercise if you don't take into account
>     everything the program in question is doing on a per transaction
>     basis.  To say that a single 2uS system call takes 25% of available
>     resources also infers that all your other code requires only 6uS
>     per transaction of overhead, which means it doesn't do very much eh?

Or that the overhead associated with what it does do is
very low because the code was cluefully written.  ;^).

-- Terry

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