Re: [PATCH][CFT] dcache-ac6-D - dcache threading

From: kumon@flab.fujitsu.co.jp
Date: Sun Jun 04 2000 - 21:34:56 EST


kuznet@ms2.inr.ac.ru writes:
> > but they are very bad for incoming traffic because it usually tends
> > to hit the same lock. Hmm....
>
> This phenomenon is known more than for year. BTW Andi, it was you who explained
> this. 8)
>
> It appeared that this ping-pong lock is washed out in real life
> due to "statistical" bucket decoupling, so that there were no reasons
> to be bothered about this.

If you mean "statistical" as "randomly distributed", this problem
actually happen in real life.

Suppose, some of the biggest ISPs provide private addresses to their
users, and users are accessing via ISP's proxy server. It is actual
environment in Japan. Usually static web pages are cachable and have
no problem.

But, when few cache disabled web pages are severely demanded, or when
users are continuously reloading the pages, the problem becomes a
real trouble.
 PlayStation2 reservation panic on last February is a candiate of
such. The random distribution hypothesis may become false there.

Or do I miss something?

--
Computer Systems Laboratory, Fujitsu Labs.
kumon@flab.fujitsu.co.jp

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