linux-kernel - Re: [PATCH v2 03/10] x86/mm: Give each mm TLB flush generation a unique ID

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Message-ID: <CALCETrXJx5c=OdNYtKJ7v3187L0r1jGuX_hfMeb76qqLGjDYxQ@mail.gmail.com>
Date:   Wed, 14 Jun 2017 10:16:19 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Dave Hansen <dave.hansen@...el.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>,
        Nadav Amit <nadav.amit@...il.com>,
        Rik van Riel <riel@...hat.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2 03/10] x86/mm: Give each mm TLB flush generation a
 unique ID

On Wed, Jun 14, 2017 at 8:54 AM, Dave Hansen <dave.hansen@...el.com> wrote:
> On 06/13/2017 09:56 PM, Andy Lutomirski wrote:
>>  typedef struct {
>> +     /*
>> +      * ctx_id uniquely identifies this mm_struct.  A ctx_id will never
>> +      * be reused, and zero is not a valid ctx_id.
>> +      */
>> +     u64 ctx_id;
>
> Ahh, and you need this because an mm itself might get reused by being
> freed and reallocated?

Exactly.  I didn't want to have to zap the data structures on each CPU
every time an mm is freed.