linux-kernel - Re: [PATCH V3 3/5] mm/hugetlb: Enable arch specific huge page size support for migration

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Message-ID: <20181024135859.GI18839@dhcp22.suse.cz>
Date:   Wed, 24 Oct 2018 15:58:59 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, suzuki.poulose@....com,
        punit.agrawal@....com, will.deacon@....com, Steven.Price@....com,
        steve.capper@....com, catalin.marinas@....com,
        akpm@...ux-foundation.org, mike.kravetz@...cle.com,
        n-horiguchi@...jp.nec.com
Subject: Re: [PATCH V3 3/5] mm/hugetlb: Enable arch specific huge page size
 support for migration

On Wed 24-10-18 15:56:39, Michal Hocko wrote:
> On Tue 23-10-18 18:31:59, Anshuman Khandual wrote:
> > Architectures like arm64 have HugeTLB page sizes which are different than
> > generic sizes at PMD, PUD, PGD level and implemented via contiguous bits.
> > At present these special size HugeTLB pages cannot be identified through
> > macros like (PMD|PUD|PGDIR)_SHIFT and hence chosen not be migrated.
> > 
> > Enabling migration support for these special HugeTLB page sizes along with
> > the generic ones (PMD|PUD|PGD) would require identifying all of them on a
> > given platform. A platform specific hook can precisely enumerate all huge
> > page sizes supported for migration. Instead of comparing against standard
> > huge page orders let hugetlb_migration_support() function call a platform
> > hook arch_hugetlb_migration_support(). Default definition for the platform
> > hook maintains existing semantics which checks standard huge page order.
> > But an architecture can choose to override the default and provide support
> > for a comprehensive set of huge page sizes.
> > 
> > Reviewed-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> > Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> 
> Acked-by: Michal Hocko <mhocko@....com>

fat fingers here, should be mhocko@...e.com of course.
-- 
Michal Hocko
SUSE Labs