Re: [PATCH 0/3] Use global pages with PTI

[Dave Hansen]

On 02/15/2018 09:47 AM, Linus Torvalds wrote:
> On Thu, Feb 15, 2018 at 5:20 AM, Dave Hansen
> <dave.hansen@xxxxxxxxxxxxxxx> wrote:
>> During the switch over to PTI, we seem to have lost our ability to have
>> GLOBAL mappings.
...
> Did you perhaps re-run any benchmark numbers just to verify? Because
> it's always good to back up patches that should improve performance
> with actual numbers..

Same test as last time except I'm using all 4 cores on a Skylake desktop
instead of just 1.  The test is this:

> https://github.com/antonblanchard/will-it-scale/blob/master/tests/lseek1.c

With PCIDs, lseek()s/second go up around 2% to 3% with the these patches
enabling the global bit (it's noisy).  I measured it at 3% before, so
definitely the same ballpark.  That was also before all of Andy's
trampoline stuff and the syscall fast path removal.