linux-kernel - Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID

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Message-ID: <CALCETrXcTG2JBnX7kwP2iM=dngk1NRf-3deSgU3BDA5rz1GuSQ@mail.gmail.com>
Date:   Thu, 22 Jun 2017 11:10:10 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Nadav Amit <nadav.amit@...il.com>
Cc:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID

On Thu, Jun 22, 2017 at 9:09 AM, Nadav Amit <nadav.amit@...il.com> wrote:
> Andy Lutomirski <luto@...nel.org> wrote:
>
>>
>> --- a/arch/x86/mm/init.c
>> +++ b/arch/x86/mm/init.c
>> @@ -812,6 +812,7 @@ void __init zone_sizes_init(void)
>>
>> DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate) = {
>>       .loaded_mm = &init_mm,
>> +     .next_asid = 1,
>
> I think this is a remainder from previous version of the patches, no? It
> does not seem necessary and may be confusing (ctx_id 0 is reserved, but not
> asid 0).

Hmm.  It's no longer needed for correctness, but init_mm still lands
in slot 0, and it seems friendly to avoid immediately stomping it.
Admittedly, this won't make any practical difference since it'll only
happen once per cpu.

>
> Other than that, if you want, you can put for the entire series:
>
> Reviewed-by: Nadav Amit <nadav.amit@...il.com>
>

Thanks!