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In-Reply-To: <92f3029f3647ab355450ed5c8252bad8cfae1e09.1640036051.git.andreyknvl@google.com>
From:   Alexander Potapenko <glider@google.com>
Date:   Tue, 21 Dec 2021 10:16:41 +0100
Message-ID: <CAG_fn=XcPT=e6zmm-B4KQPLujpuC9D+hTbJEsua31onzopDT5g@mail.gmail.com>
Subject: Re: [PATCH mm v4 07/39] mm: clarify __GFP_ZEROTAGS comment
To:     andrey.konovalov@linux.dev
Cc:     Marco Elver <elver@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Peter Collingbourne <pcc@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrey Konovalov <andreyknvl@google.com>
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On Mon, Dec 20, 2021 at 10:59 PM <andrey.konovalov@linux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@google.com>

Reviewed-by: Alexander Potapenko <glider@google.com>

>
> __GFP_ZEROTAGS is intended as an optimization: if memory is zeroed during
> allocation, it's possible to set memory tags at the same time with little
> performance impact.
Perhaps you could mention this intention explicitly in the comment?
Right now it still doesn't reference performance.

>
> Clarify this intention of __GFP_ZEROTAGS in the comment.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
>  include/linux/gfp.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 0b2d2a636164..d6a184523ca2 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -228,8 +228,8 @@ struct vm_area_struct;
>   *
>   * %__GFP_ZERO returns a zeroed page on success.
>   *
> - * %__GFP_ZEROTAGS returns a page with zeroed memory tags on success, if
> - * __GFP_ZERO is set.
> + * %__GFP_ZEROTAGS zeroes memory tags at allocation time if the memory i=
tself
> + * is being zeroed (either via __GFP_ZERO or via init_on_alloc).
>   *
>   * %__GFP_SKIP_KASAN_POISON returns a page which does not need to be poi=
soned
>   * on deallocation. Typically used for userspace pages. Currently only h=
as an
> --
> 2.25.1
>
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Alexander Potapenko
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