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Date:   Tue, 17 Jan 2023 19:21:18 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>, x86@kernel.org,
        Kostya Serebryany <kcc@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Taras Madan <tarasmadan@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        "H . J . Lu" <hjl.tools@gmail.com>,
        Andi Kleen <ak@linux.intel.com>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        Bharata B Rao <bharata@amd.com>,
        Jacob Pan <jacob.jun.pan@linux.intel.com>,
        Ashok Raj <ashok.raj@intel.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Sami Tolvanen <samitolvanen@google.com>,
        ndesaulniers@google.com, joao@overdrivepizza.com
Subject: Re: [PATCHv14 08/17] x86/mm: Reduce untagged_addr() overhead until
 the first LAM user
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On Tue, Jan 17, 2023 at 09:18:01AM -0800, Linus Torvalds wrote:

> But maybe even those aren't worth worrying about. At least they do the
> unmasking outside the loop - although then in the case of execve(),
> the string copies themselves are obviously done in a loop anyway.
> 
> Kirill, do you have clear numbers for that static key being a noticeable win?

Numbers would be good; I think this all started as a precaution, but
clearly that's not really working out so well :/