linux-kernel - Re: [RFC] mm:add KPF_ZERO_PAGE flag for /proc/kpageflags

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Date:	Fri, 5 Dec 2014 13:20:37 +0400
From:	Konstantin Khlebnikov <koct9i@...il.com>
To:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"n-horiguchi@...jp.nec.com" <n-horiguchi@...jp.nec.com>
Subject: Re: [RFC] mm:add KPF_ZERO_PAGE flag for /proc/kpageflags

On Fri, Dec 5, 2014 at 11:57 AM, Wang, Yalin <Yalin.Wang@...ymobile.com> wrote:
> This patch add KPF_ZERO_PAGE flag for zero_page,
> so that userspace process can notice zero_page from
> /proc/kpageflags, and then do memory analysis more accurately.

It would be nice to mark also huge_zero_page. See (completely
untested) patch in attachment.

>
> Signed-off-by: Yalin Wang <yalin.wang@...ymobile.com>
> ---
>  fs/proc/page.c                         | 3 +++
>  include/uapi/linux/kernel-page-flags.h | 1 +
>  2 files changed, 4 insertions(+)
>
> diff --git a/fs/proc/page.c b/fs/proc/page.c
> index 1e3187d..120dbf7 100644
> --- a/fs/proc/page.c
> +++ b/fs/proc/page.c
> @@ -136,6 +136,9 @@ u64 stable_page_flags(struct page *page)
>         if (PageBalloon(page))
>                 u |= 1 << KPF_BALLOON;
>
> +       if (is_zero_pfn(page_to_pfn(page)))
> +               u |= 1 << KPF_ZERO_PAGE;
> +
>         u |= kpf_copy_bit(k, KPF_LOCKED,        PG_locked);
>
>         u |= kpf_copy_bit(k, KPF_SLAB,          PG_slab);
> diff --git a/include/uapi/linux/kernel-page-flags.h b/include/uapi/linux/kernel-page-flags.h
> index 2f96d23..a6c4962 100644
> --- a/include/uapi/linux/kernel-page-flags.h
> +++ b/include/uapi/linux/kernel-page-flags.h
> @@ -32,6 +32,7 @@
>  #define KPF_KSM                        21
>  #define KPF_THP                        22
>  #define KPF_BALLOON            23
> +#define KPF_ZERO_PAGE          24
>
>
>  #endif /* _UAPILINUX_KERNEL_PAGE_FLAGS_H */
> --
> 2.1.3

Download attachment "kpageflags-zero-huge-page" of type "application/octet-stream" (2626 bytes)