Messages in this thread |  | | From | Linus Torvalds <> | Date | Wed, 1 Nov 2017 15:28:48 -0700 | Subject | Re: [PATCH 00/23] KAISER: unmap most of the kernel from userspace page tables |
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On Wed, Nov 1, 2017 at 3:14 PM, Dave Hansen <dave.hansen@linux.intel.com> wrote: > > I ran some quick tests. When CONFIG_KAISER=y, but "echo 0 > > kaiser-enabled", the tests that I ran were within the noise vs. a > vanilla kernel, and that's with *zero* optimization.
I guess the optimal version just ends up switching between two different entrypoints for the on/off case.
And the not-quite-as-aggressive, but almost-optimal version would just be a two-byte asm alternative with an unconditional branch to the movcr3 code and back, and is turned into a noop when it's off.
But since 99%+ of the cost is going to be that cr3 write, even the stupid "just load value and branch over the cr3 conditionally" is going to make things hard to measure.
Linus
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