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Date:      Fri, 28 Jul 2006 14:47:01 +0100
From:      Brian Candler <B.Candler@pobox.com>
To:        John Baldwin <jhb@freebsd.org>
Cc:        freebsd-current@freebsd.org, Oliver Fromme <olli@lurza.secnetix.de>
Subject:   Re: vmstat's entries type
Message-ID:  <20060728134701.GA45273@uk.tiscali.com>
In-Reply-To: <200607280928.36573.jhb@freebsd.org>
References:  <200607251254.k6PCsBef092737@lurza.secnetix.de> <200607271058.13055.jhb@freebsd.org> <20060728121525.GA44917@uk.tiscali.com> <200607280928.36573.jhb@freebsd.org>

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On Fri, Jul 28, 2006 at 09:28:36AM -0400, John Baldwin wrote:
> 	lock incl counter
> 	jnc 1f
> 	lock incl counter+4
> 1:

That looks safe to me. How expensive is a forward jump like that, i.e. do
you get a pipeline bubble?

The 'polling' argument says just do

    lock incl counter

and poll all counters every 5 minutes, looking for a wrap. I think that's
almost certainly going to be cheaper, as long as you can keep track of where
all these counters are located.

Regards,

Brian.


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