From: Michal Hocko <mhocko@kernel.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Ashish Mhetre <amhetre@nvidia.com>,
linux-mm@kvack.org, akpm@linux-foundation.org, vdumpa@nvidia.com,
Snikam@nvidia.com
Subject: Re: [PATCH] mm: Disable movable allocation for TRANSHUGE pages
Date: Tue, 25 Sep 2018 23:11:23 +0200 [thread overview]
Message-ID: <20180925211123.GZ18685@dhcp22.suse.cz> (raw)
In-Reply-To: <20180925210001.j4olzx3fru4jpfys@kshutemo-mobl1>
On Wed 26-09-18 00:00:02, Kirill A. Shutemov wrote:
> On Tue, Sep 25, 2018 at 08:30:19PM +0200, Michal Hocko wrote:
> > On Tue 25-09-18 14:51:53, Kirill A. Shutemov wrote:
> > > On Tue, Sep 25, 2018 at 12:55:33PM +0530, Ashish Mhetre wrote:
> > > > TRANSHUGE pages have no migration support.
> > >
> > > Transparent pages have migration support since v4.14.
> >
> > This is true but not for all architectures AFAICS. In fact git grep
> > suggests that only x86 supports the migration. So unless I am missing
> > something the patch has some merit.
>
> THP pages are movable from the beginning. Before 4.14, the cost of
> migration was THP split. From my PoV __GFP_MOVABLE is justified and we
> should keep it there.
A very good point! I haven't really looked closer to what happens in the
cma/migration code when the migration is not supported. As you've said
THP migt be split into 4kB pages and those are migrateable by
definition. So I take back my proposal and if this doesn't work properly
now then it should really be handled by splitting up the thp.
Thanks and sorry I've missed this!
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2018-09-25 21:11 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-25 7:25 Ashish Mhetre
2018-09-25 11:51 ` Kirill A. Shutemov
2018-09-25 18:30 ` Michal Hocko
2018-09-25 21:00 ` Kirill A. Shutemov
2018-09-25 21:11 ` Michal Hocko [this message]
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