On 09/29/2012 06:48 AM, Andrea Arcangeli wrote:

There would be a small cache benefit here... but even then some first
level caches are virtually indexed IIRC (always physically tagged to
avoid the software to notice) and virtually indexed ones won't get any
benefit.

Not quite.  The virtual indexing is limited to a few bits (e.g. three
bits on K8); the right way to deal with that is to color the zeropage,
both the regular one and the virtual one (the virtual one would circle
through all the colors repeatedly.)

The cache difference, therefore, is *huge*.

I guess it won't make a whole lot of difference but my preference is
for the previous implementation that always guaranteed huge TLB
entries whenever possible. Said that I'm fine either ways so if
somebody has strong reasons for wanting this one, I'd like to hear
about it.

It's a performance tradeoff, and it can, and should, be measured.

	-hpa

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