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Date: Thu, 17 Dec 2009 19:28:08 +1100 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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Cc: Harti Brandt <harti@FreeBSD.org>, John Baldwin <jhb@FreeBSD.org>,
	freebsd-arch@FreeBSD.org
Subject: Re: network statistics in SMP
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On Thu, 17 Dec 2009, Bruce Evans wrote:

> On Thu, 17 Dec 2009, Bruce Evans wrote:
>
>> ...
> Actually3, the generation count can be per-CPU and accessed without atomic
> ops (provided reads of it on other CPUs return a consistent possibly-stale
> value).
>
>> Simple version:
>
> Better version:
> ...

Duh, this is far too complicated and bloated.  Counters can be their own
generation counts -- you just read them again to see if they are quiescent.
A heavyweight sync before each of the (sets of) reads is still necessary.
Self-generation counters give a separate generation counter for each
normal counter, so quiescence can be easily be checked for and/or enforced 
per-counter.

Bruce