Re: [patch 55/60] x86/mm: Use INVPCID for __native_flush_tlb_single()

[Andy Lutomirski]

On Mon, Dec 4, 2017 at 6:08 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
>
> This uses INVPCID to shoot down individual lines of the user mapping
> instead of marking the entire user map as invalid. This
> could/might/possibly be faster.
>
> This for sure needs tlb_single_page_flush_ceiling to be redetermined;
> esp. since INVPCID is _slow_.

I'm wondering if INVPCID is *so* slow that this patch is entirely
counterproductive.

--Andy