Re: [patch] SMP alternatives

From: Alan Cox
Date: Wed Nov 23 2005 - 16:32:50 EST

On Mer, 2005-11-23 at 22:13 +0100, Andi Kleen wrote:
> The idea was to turn LOCK on only if the process has any
> shared writable mapping and num_online_cpus() > 0.

That makes a lot of sense, and if we hit hardware that does funky stuff
then the driver can set a 'vma needs lock' bit for the same effect.

> Might be a bit costly to rewrite all the page tables for that case
> just to change the PAT index. A bit is nicer for that.

CPU insert/remove is performed how many times a second ? Or for that
matter why not just reload the PAT register and keep the index the
same ?

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