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Re: [Xen-devel] [PATCH] respin of mprotect performance patch

On Sat, 12 Jan 2008 20:08:06 -0700
"Bruce Rogers" <brogers@xxxxxxxxxx> wrote:

> I made a few tweaks to your patch as follows:
> As I see it we need to preserve the existing AD bits but additionally OR in 
> the AD bits being passed in (see behavior of pte_modify(), where it preserves 
> current AD in use of _PAGE_CHG_MASK along with ORing in newprot bits, which 
> include AD bits (A at least).)
> See update_intpte() for this change.
> Also we need to remove cmd value from req.ptr in do_mmu_update..
> Updated Linux patch is also included.
> Let me know if I'm missing the point some how.

I tested a quick backport of these patches to XEN 3.1.2 and
kernel 2.6.18.

Unfortunately, performance and scalability do not seem to
have improved with these patches, with the SAP mprotect 
test program.  I do not know why - maybe their program
calls mprotect with really small areas so the batching
does not do much?

This is on a quad CPU Intel x86-64 system.

All rights reversed.

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