From: Andrew Morton <akpm@linux-foundation.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC] mm/migrate: Add new migration reason MR_HUGETLB
Date: Wed, 31 Jan 2018 12:12:17 -0800 [thread overview]
Message-ID: <20180131121217.4c80263d68a4ad4da7b170f0@linux-foundation.org> (raw)
In-Reply-To: <20180131075852.GL21609@dhcp22.suse.cz>
On Wed, 31 Jan 2018 08:58:52 +0100 Michal Hocko <mhocko@kernel.org> wrote:
> On Wed 31-01-18 07:55:05, Anshuman Khandual wrote:
> > On 01/30/2018 01:29 PM, Michal Hocko wrote:
> > > On Tue 30-01-18 08:37:14, Anshuman Khandual wrote:
> > >> alloc_contig_range() initiates compaction and eventual migration for
> > >> the purpose of either CMA or HugeTLB allocation. At present, reason
> > >> code remains the same MR_CMA for either of those cases. Lets add a
> > >> new reason code which will differentiate the purpose of migration
> > >> as HugeTLB allocation instead.
> > > Why do we need it?
> >
> > The same reason why we have MR_CMA (maybe some other ones as well) at
> > present, for reporting purpose through traces at the least. It just
> > seemed like same reason code is being used for two different purpose
> > of migration.
>
> But do we have any real user asking for this kind of information?
It seems a reasonable cleanup: reusing MR_CMA for hugetlb just because
it happens to do the right thing is a bit hacky - the two things aren't
particularly related and a reader could be excused for feeling
confusion.
But the change seems incomplete:
> + if (migratetype == MIGRATE_CMA)
> + migrate_reason = MR_CMA;
> + else
> + migrate_reason = MR_HUGETLB;
If we're going to do this cleanup then shouldn't we go all the way and
add MIGRATE_HUGETLB?
Alternatively... instead of adding MR_HUGETLB (and perhaps
MIGRATE_HUGETLB), can we identify what characteristics these two things
have in common and invent a new, more generic identifier? So that both
migrate-for-CMA and migrate-for-HUGETLB will use MIGRATE_NEWNAME and
MR_NEWNAME?
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next prev parent reply other threads:[~2018-01-31 20:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-30 3:07 [RFC] mm/migrate: Add new migration reason MR_HUGETLB Anshuman Khandual
2018-01-30 5:16 ` Anshuman Khandual
2018-01-30 7:59 ` Michal Hocko
2018-01-31 2:25 ` Anshuman Khandual
2018-01-31 2:40 ` Mike Kravetz
2018-01-31 7:58 ` Michal Hocko
2018-01-31 20:12 ` Andrew Morton [this message]
2018-01-31 20:32 ` Michal Hocko
2018-02-01 8:28 ` Anshuman Khandual
2018-02-02 9:15 ` [PATCH] mm/migrate: Change migration reason MR_CMA as MR_CONTIG_RANGE Anshuman Khandual
2018-02-02 9:36 ` Michal Hocko
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