linux-kernel - Re: [PATCH v3 5/9] x86/mm/tlb: Privatize cpu

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Message-ID: <5c4b7bd2-ea0e-dc8d-edbb-1b1b739b963e@intel.com>
Date:   Fri, 19 Jul 2019 11:48:13 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Nadav Amit <namit@...are.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v3 5/9] x86/mm/tlb: Privatize cpu_tlbstate

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.