svn commit: r252032 - head/sys/amd64/include

[Dmitry Morozovsky]

On Wed, 26 Jun 2013, Gleb Smirnoff wrote:

> On Wed, Jun 26, 2013 at 11:42:39AM +1000, Bruce Evans wrote:
> B> > Anyway, as Gleb said, there is no point in
> B> > optimizing the i386 kernel.
> B> 
> B> I said that there is every point in optimizing the i386 kernel.  This
> B> applies even more to other 32-bit arches.  Some CPUs are much slower
> B> than modern x86's.  They shouldn't be slowed down more by inefficient
> B> KPIs.
> 
> I didn't mean that i386 arch is a relic and should be ignored at all.
> 
> What I actually meant, is that the problem of performance drop due to
> cache poisoning and loss of statistics with simple "+=" operation can
> be observed only at extremely high event rates, with multiple processors
> involved.
> 
> The counter(9) is solution for these conditions. Thus we are interested
> in optimising amd64, not i386. The latter isn't affected neither positively
> nor negatively with these changes, just because last i386 CPUs can't reach
> the event rates where need for counter(9) arises. Yes, you can tweak
> implementation and obtain better results with microbenchmarks, but I bet
> that any change in counter(9) implementation won't affect packet forwarding
> rate on any i386. What we claim for i386 (and all other arches) that
> counter(9) is lossless, and that's all.
> 
> I second to Konstantin, that we don't have objections in any changes to
> i386 part of counter, including a daemon, but the changes shouldn't affect
> amd64.

Ah, apparently this mostly answers the question I've just asked ;)

-- 
Sincerely,
D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
[ FreeBSD committer:                                 marck at FreeBSD.org ]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck at rinet.ru ***
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