Re: [PATCH v3 5/9] x86/mm/tlb: Privatize cpu_tlbstate

[Nadav Amit]

> On Jul 19, 2019, at 11:48 AM, Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
> 
> On 7/19/19 11:43 AM, Nadav Amit wrote:
>> Andy said that for the lazy tlb optimizations there might soon be more
>> shared state. If you prefer, I can move is_lazy outside of tlb_state, and
>> not set it in any alternative struct.
> 
> I just wanted to make sure that we capture these rules:
> 
> 1. If the data is only ever accessed on the "owning" CPU via
>   this_cpu_*(), put it in 'tlb_state'.
> 2. If the data is read by other CPUs, put it in 'tlb_state_shared'.
> 
> I actually like the idea of having two structs.

Yes, thatâs exactly the idea. In the (1) case, we may even be able to mark
the struct with __thread qualifier, which IIRC would prevent memory barriers
from causing these values being reread.