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Date: Mon, 24 Jul 2006 02:03:50 +0200
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Cc: freebsd-current@freebsd.org
Subject: Re: vmstat's entries type
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sthaug@nethelp.no wrote:
>>> One approach that we could use for 64-bit counters would be to just
>>> use 32-bits one, and poll them for overflow and bump an overflow
>>> count.  This assumes that the 32-bit counters overflow much less ofte=
n
>>> than the polling interval, and easily triples the amount of storage
>>> for each of them...  It is ugly :-(
>>>
>> What's wrong with the add+adc (asm) approach found on any i386?
>=20
> Presumably the fact that add + adc isn't an atomic operation. So if
> you want to guarantee 64 bit consistency, you need locking or similar.
>=20

Would it not be necessary to do this locking anyway?
I don't see how polling for overflow would help this consistency.
Are both suggestions insufficient?

--=20
Sten Daniel S=F8rsdal