linux-kernel - Re: [HMM 08/15] mm/ZONE_DEVICE: special case put

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Message-ID: <20170523132317.rfg33zwfbx3zl6be@node.shutemov.name>
Date:   Tue, 23 May 2017 16:23:17 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Jérôme Glisse <jglisse@...hat.com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, John Hubbard <jhubbard@...dia.com>,
        David Nellans <dnellans@...dia.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [HMM 08/15] mm/ZONE_DEVICE: special case put_page() for device
 private pages

On Mon, May 22, 2017 at 12:51:59PM -0400, Jérôme Glisse wrote:
> A ZONE_DEVICE page that reach a refcount of 1 is free ie no longer
> have any user. For device private pages this is important to catch
> and thus we need to special case put_page() for this.
> 
> Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
> ---
>  include/linux/mm.h | 30 ++++++++++++++++++++++++++++++
>  kernel/memremap.c  |  1 -
>  2 files changed, 30 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index a825dab..11f7bac 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -23,6 +23,7 @@
>  #include <linux/page_ext.h>
>  #include <linux/err.h>
>  #include <linux/page_ref.h>
> +#include <linux/memremap.h>
>  
>  struct mempolicy;
>  struct anon_vma;
> @@ -795,6 +796,20 @@ static inline bool is_device_private_page(const struct page *page)
>  	return ((page_zonenum(page) == ZONE_DEVICE) &&
>  		(page->pgmap->type == MEMORY_DEVICE_PRIVATE));
>  }
> +
> +static inline void put_zone_device_private_page(struct page *page)

Could you measure how much bloat this change produce?

I would rather make put_zone_device_private_page() non-inline. put_page()
is inlined everewhere. It's beneficial to keep it skinny.

(And I guess it would help solving 0-day reporeted build issue).

-- 
 Kirill A. Shutemov