PCID and TLB flushes (was: [GIT PULL] kdbus for 4.1-rc1)

From: Kirill A. Shutemov
Date: Tue Apr 28 2015 - 18:16:19 EST

On Tue, Apr 28, 2015 at 01:42:10PM -0700, Andy Lutomirski wrote:
> At some point, I'd like to implement PCID on x86 (if no one beats me
> to it, and this is a low priority for me), which will allow us to skip
> expensive TLB flushes while context switching. I have no idea whether
> ARM can do something similar.

I talked with Dave about implementing PCID and he thinks that it will be
net loss. TLB entries will live longer and it means we would need to trigger
more IPIs to flash them out when we have to. Cost of IPIs will be higher
than benifit from hot TLB after context switch.

Do you have different expectations?

Kirill A. Shutemov
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/