Re: [PATCH mm v4 07/39] mm: clarify __GFP_ZEROTAGS comment

Alexander Potapenko
2021-12-21T09:17:19Z

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 itself
> + * 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 poisoned
> * on deallocation. Typically used for userspace pages. Currently only has an
> --
> 2.25.1
>
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--
Alexander Potapenko
Software Engineer

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