Re: [PATCH] mm: Change of refcounting method for compound page.

["Radosław Smogura" <mail@smogura.eu>]

Dnia piątek, 3 lutego 2012 o 18:28:13 Radosław Smogura napisał(a):
> Compound pages are now refcounted in way allowing tracking of tail pages
> and automatically free of compound page when all references (counter)
> fell to zero. This in addition make get_page and get_page_unless_zero
> similar in work, as well put_page and put_page_unless_zero. In addition
> it  makes procedures more friendly. One thing that should be taken, by
> developer, on account is to take care when page is putted or geted when
> compound lock is obtained, to avoid deadlocks. Locking is used to
> prevent concurrent compound split and only when page refcount goes from
> 0 to 1 or vice versa.
> 
> Technically implementation uses 3rd element of compound page to store
> "tails usage counter". This counter is decremented when tail pages count
> goes to zero, and bumped when tail page is getted from zero usage
> (recovered) – this is to keep backward compatible usage of tail pages.
> If "tails usage counter" fell to zero head counter is decremented, if
> "tails usage counter" is increased to one the head count is increased,
> too. For compound pages without 3rd element (order of 1, two pages) 2nd
> page count is used in similar way as for higher order pages.
> 
> Signed-off-by: Radosław Smogura <mail@smogura.eu>
> ---
>  include/linux/mm.h       |   94 ++++++++++++-----
>  include/linux/mm_types.h |   24 ++++-
>  include/linux/pagemap.h  |    1 -
>  mm/huge_memory.c         |   25 +----
>  mm/internal.h            |   46 ---------
>  mm/memory.c              |    2 +-
>  mm/page_alloc.c          |    2 +
>  mm/swap.c                |  254
> +++++++++++++++++++++++++++++----------------- 8 files changed, 256
> insertions(+), 192 deletions(-)
<snip>
I would like to say huge sorry, I sent wrong patch (yesterday work). Please 
discard previous patch, and consider patch I will send in reply to this email. 
Not included change was introduced to allow proper concurrent work of get/put 
page and split page .

Regards,
Radosław Smogura

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