linux-kernel - Re: [PATCHv5 4/7] mm: pack compound_dtor and compound

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Message-ID: <55F15064.9040507@suse.cz>
Date:	Thu, 10 Sep 2015 11:41:56 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv5 4/7] mm: pack compound_dtor and compound_order into one
 word in struct page

On 09/03/2015 02:35 PM, Kirill A. Shutemov wrote:
> The patch halves space occupied by compound_dtor and compound_order in
> struct page.
> 
> For compound_order, it's trivial long -> short conversion.
> 
> For get_compound_page_dtor(), we now use hardcoded table for destructor
> lookup and store its index in the struct page instead of direct pointer
> to destructor. It shouldn't be a big trouble to maintain the table: we
> have only two destructor and NULL currently.
> 
> This patch free up one word in tail pages for reuse. This is preparation
> for the next patch.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Reviewed-by: Michal Hocko <mhocko@...e.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

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