On Thu, Dec 06, 2001 at 09:10:15AM -0500, Arjan van de Ven wrote:
> On Thu, Dec 06, 2001 at 07:39:40PM +0530, Ravikiran G Thirumalai wrote:
> > 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.
If it is a low frequency statistics then the expensive access wouldn't
really matter much, right ? On the other hand, this will likely help
specially with larger number of CPUs.
>
> There's several things where per cpu data is useful; low frequency
> statistics is not one of them in my opinion.
It is quite possible that you are right. What we need to do is
a measurement effort to understand the impact.
Thanks
Dipankar
-- Dipankar Sarma <dipankar@in.ibm.com> http://lse.sourceforge.net Linux Technology Center, IBM Software Lab, Bangalore, India. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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