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

[Vlastimil Babka]

On 02/04/2016 07:02 AM, Joonsoo Kim wrote:
> 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().

Hm, right, thanks for catching this. I admit I didn't try disabling 
compaction during the tests.

> Thanks.