Re: [Lse-tech] [RFC] [PATCH] Scalable Statistics Counters

Arjan van de Ven (arjanv@redhat.com)
Thu, 6 Dec 2001 09:10:15 -0500


On Thu, Dec 06, 2001 at 07:39:40PM +0530, Ravikiran G Thirumalai wrote:
> Well, as I mentioned in my earlier post, we have performed
> "micro benchmarking", which does not reflect the actual run time
> kernel conditions. I guess u gotta take these results with a
> pinch of salt.
>
> But, you cannot deny that there r gonna be a lot of cacheline
> invalidations, if you use a global counter. Using per-cpu versions is
> definitely going to improve kernel performance.

there's not that many counters in fact. And if you care about a gige
counter, just bind the card to a specific CPU and you have ad-hoc per-cpu
counters...

The extra cost of getting to them (extra indirection) makes each access
more expensive..... in the end it might be a loss.

There's several things where per cpu data is useful; low frequency
statistics is not one of them in my opinion.

Greetings,
Arjan van de Ven
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