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Date: Sun, 9 Dec 2001 00:46:22 +1100
From: Anton Blanchard <anton@samba.org>
To: Niels Christiansen <nchr@us.ibm.com>
Cc: kiran@linux.ibm.com, lse-tech@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [Lse-tech] [RFC] [PATCH] Scalable Statistics Counters
Message-ID: <20011208134622.GD2418@krispykreme>
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Hi,

> > There's several things where per cpu data is useful; low frequency
> > statistics is not one of them in my opinion.
> 
> ...which may be true for 4-ways and even 8-ways but when you get to
> 32-ways and greater, you start seeing cache problems.  That was the
> case on AIX and per-cpu counters was one of the changes that helped
> get the spectacular scalability on Regatta.

I agree there are large areas of improvement to be done wrt cacheline
ping ponging (see my patch in 2.4.17-pre6 for one example), but we
should do our own benchmarking and not look at what AIX has been doing.

Anton
(ppc64 Linux Hacker)
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