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From: Michal Mertl <mime@traveller.cz>
To: Paul Allen <nospam@ugcs.caltech.edu>
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Date: Sun, 30 Jul 2006 01:50:36 +0200
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Cc: Peter Jeremy <peterjeremy@optushome.com.au>, freebsd-current@freebsd.org,
	Brian Candler <B.Candler@pobox.com>
Subject: Re: vmstat's entries type
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Michal Mertl wrote:
> Paul Allen wrote:
> > Surely all you need to do is a cheap crit_enter,crit_exit 
> > while updating the 64-bit per cpu counters.  and on
> > a 64-bit arch you skip the crit_enter,crit_exit.
> 
> Critical_enter/exit seem to be quite lightweight (single
> read/modify/write of a variable).

One more question. Why do you say that crit_* can be avoided on 64-bit
arch? If the reason was that "increment of a 64 bit number is one
operation there" it probably is not true - as somebody already stated,
some instruction sets don't allow atomic increment of a memory location.

Michal