linux-kernel - Re: [PATCH 2/2] mm: rename and move get/set_freepage

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Message-ID: <20150723052431.GD4449@js1304-P5Q-DELUXE>
Date:	Thu, 23 Jul 2015 14:24:31 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	"minkyung88.kim" <minkyung88.kim@....com>, kmk3210@...il.com,
	Seungho Park <seungho1.park@....com>,
	Minchan Kim <minchan@...nel.org>,
	Michal Nazarewicz <mina86@...a86.com>,
	Laura Abbott <lauraa@...eaurora.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 2/2] mm: rename and move get/set_freepage_migratetype

On Wed, Jul 22, 2015 at 02:29:08PM +0200, Vlastimil Babka wrote:
> On 07/21/2015 02:53 PM, Vlastimil Babka wrote:
> > The pair of get/set_freepage_migratetype() functions are used to cache
> > pageblock migratetype for a page put on a pcplist, so that it does not have
> > to be retrieved again when the page is put on a free list (e.g. when pcplists
> > become full). Historically it was also assumed that the value is accurate for
> > pages on freelists (as the functions' names unfortunately suggest), but that
> > cannot be guaranteed without affecting various allocator fast paths. It is in
> > fact not needed and all such uses have been removed.
> > 
> > The last remaining (but pointless) usage related to pages of freelists is in
> > move_freepages(), which this patch removes.
> 
> I realized there's one more callsite that can be removed. Here's
> whole updated patch due to different changelog and to cope with
> context changed by the fixlet to patch 1/2.
> 
> ------8<------
> From: Vlastimil Babka <vbabka@...e.cz>
> Date: Thu, 2 Jul 2015 16:37:06 +0200
> Subject: mm: rename and move get/set_freepage_migratetype
> 
> The pair of get/set_freepage_migratetype() functions are used to cache
> pageblock migratetype for a page put on a pcplist, so that it does not have
> to be retrieved again when the page is put on a free list (e.g. when pcplists
> become full). Historically it was also assumed that the value is accurate for
> pages on freelists (as the functions' names unfortunately suggest), but that
> cannot be guaranteed without affecting various allocator fast paths. It is in
> fact not needed and all such uses have been removed.
> 
> The last two remaining (but pointless) usages related to pages of freelists
> are removed by this patch:
> - move_freepages() which operates on pages already on freelists
> - __free_pages_ok() which puts a page directly to freelist, bypassing pcplists
> 
> To prevent further confusion, rename the functions to
> get/set_pcppage_migratetype() and expand their description. Since all the
> users are now in mm/page_alloc.c, move the functions there from the shared
> header.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> Acked-by: David Rientjes <rientjes@...gle.com>

Acked-by: Joonsoo Kim <iamjoonsoo.kim@....com>

Thanks.
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