linux-kernel - Re: [PATCH] mm, hugetlb: don't require CMA for runtime gigantic pages

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Date:	Thu, 4 Feb 2016 15:02:21 +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,
	Luiz Capitulino <lcapitulino@...hat.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Davidlohr Bueso <dave@...olabs.net>,
	Hillf Danton <hillf.zj@...baba-inc.com>,
	Mike Kravetz <mike.kravetz@...cle.com>
Subject: Re: [PATCH] mm, hugetlb: don't require CMA for runtime gigantic pages

On Wed, Feb 03, 2016 at 06:50:11PM +0100, Vlastimil Babka wrote:
> Commit 944d9fec8d7a ("hugetlb: add support for gigantic page allocation at
> runtime") has added the runtime gigantic page allocation via
> alloc_contig_range(), making this support available only when CONFIG_CMA is
> enabled. Because it doesn't depend on MIGRATE_CMA pageblocks and the
> associated infrastructure, it is possible with few simple adjustments to
> require only CONFIG_MEMORY_ISOLATION instead of full CONFIG_CMA.
> 
> After this patch, alloc_contig_range() and related functions are available
> and used for gigantic pages with just CONFIG_MEMORY_ISOLATION enabled. Note
> CONFIG_CMA selects CONFIG_MEMORY_ISOLATION. This allows supporting runtime
> gigantic pages without the CMA-specific checks in page allocator fastpaths.

You need to set CONFIG_COMPACTION or CONFIG_CMA to use
isolate_migratepages_range() and others in alloc_contig_range().

Thanks.