From: Joonsoo Kim <js1304@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux Memory Management List <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team@lge.com, Vlastimil Babka <vbabka@suse.cz>,
Christoph Hellwig <hch@infradead.org>,
Roman Gushchin <guro@fb.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH v3 4/8] mm/hugetlb: make hugetlb migration callback CMA aware
Date: Mon, 29 Jun 2020 15:27:25 +0900 [thread overview]
Message-ID: <CAAmzW4NLVwvqtoUb+JJ+WV=7_n800vA+YYC0LyrDS6iQ7wxcdg@mail.gmail.com> (raw)
In-Reply-To: <20200626072324.GT1320@dhcp22.suse.cz>
2020년 6월 26일 (금) 오후 4:23, Michal Hocko <mhocko@kernel.org>님이 작성:
>
> On Fri 26-06-20 13:49:15, Joonsoo Kim wrote:
> > 2020년 6월 25일 (목) 오후 8:54, Michal Hocko <mhocko@kernel.org>님이 작성:
> > >
> > > On Tue 23-06-20 15:13:44, Joonsoo Kim wrote:
> > > > From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> > > >
> > > > new_non_cma_page() in gup.c which try to allocate migration target page
> > > > requires to allocate the new page that is not on the CMA area.
> > > > new_non_cma_page() implements it by removing __GFP_MOVABLE flag. This way
> > > > works well for THP page or normal page but not for hugetlb page.
> > >
> > > Could you explain why? I mean why cannot you simply remove __GFP_MOVABLE
> > > flag when calling alloc_huge_page_nodemask and check for it in dequeue
> > > path?
> >
> > If we remove __GFP_MOVABLE when calling alloc_huge_page_nodemask, we cannot
> > use the page in ZONE_MOVABLE on dequeing.
> >
> > __GFP_MOVABLE is not only used for CMA selector but also used for zone
> > selector. If we clear it, we cannot use the page in the ZONE_MOVABLE
> > even if it's not CMA pages. For THP page or normal page allocation,
> > there is no way to avoid this weakness without introducing another
> > flag or argument. For me, introducing another flag or argument for
> > these functions looks over-engineering so I don't change them and
> > leave them as they are (removing __GFP_MOVABLE).
> >
> > But, for alloc_huge_page_nodemask(), introducing a new argument
> > doesn't seem to be a problem since it is not a general function but
> > just a migration target allocation function.
>
> I really do not see why hugetlb and only the dequeing part should be
> special. This just leads to a confusion. From the code point of view it
> makes perfect sense to opt out CMA regions for !__GFP_MOVABLE when
> dequeing. So I would rather see a consistent behavior than a special
> case deep in the hugetlb allocator layer.
It seems that there is a misunderstanding. It's possible to opt out CMA regions
for !__GFP_MOVABLE when dequeing. It's reasonable. But, for !__GFP_MOVABLE,
we don't search the hugetlb page on the ZONE_MOVABLE when dequeing since
dequeing zone is limited by gfp_zone(gfp_mask). Solution that Introduces a new
argument doesn't cause this problem while avoiding CMA regions.
Thanks.
next prev parent reply other threads:[~2020-06-29 20:40 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 6:13 [PATCH v3 0/8] clean-up the migration target allocation functions js1304
2020-06-23 6:13 ` [PATCH v3 1/8] mm/page_isolation: prefer the node of the source page js1304
2020-06-23 6:13 ` [PATCH v3 2/8] mm/migrate: move migration helper from .h to .c js1304
2020-06-23 6:13 ` [PATCH v3 3/8] mm/hugetlb: unify migration callbacks js1304
2020-06-24 21:18 ` Mike Kravetz
2020-06-25 11:26 ` Michal Hocko
2020-06-26 4:02 ` Joonsoo Kim
2020-07-02 16:13 ` Vlastimil Babka
2020-07-03 0:55 ` Joonsoo Kim
2020-06-23 6:13 ` [PATCH v3 4/8] mm/hugetlb: make hugetlb migration callback CMA aware js1304
2020-06-25 11:54 ` Michal Hocko
2020-06-26 4:49 ` Joonsoo Kim
2020-06-26 7:23 ` Michal Hocko
2020-06-29 6:27 ` Joonsoo Kim [this message]
2020-06-29 7:55 ` Michal Hocko
2020-06-30 6:30 ` Joonsoo Kim
2020-06-30 6:42 ` Michal Hocko
2020-06-30 7:22 ` Joonsoo Kim
2020-06-30 16:37 ` Mike Kravetz
2020-06-23 6:13 ` [PATCH v3 5/8] mm/migrate: make a standard migration target allocation function js1304
2020-06-25 12:05 ` Michal Hocko
2020-06-26 5:02 ` Joonsoo Kim
2020-06-26 7:33 ` Michal Hocko
2020-06-29 6:41 ` Joonsoo Kim
2020-06-29 8:03 ` Michal Hocko
2020-06-30 7:19 ` Joonsoo Kim
2020-07-03 15:25 ` Vlastimil Babka
2020-06-23 6:13 ` [PATCH v3 6/8] mm/gup: use a standard migration target allocation callback js1304
2020-06-25 12:08 ` Michal Hocko
2020-06-26 5:03 ` Joonsoo Kim
2020-07-03 15:56 ` Vlastimil Babka
2020-07-06 8:34 ` Joonsoo Kim
2020-06-23 6:13 ` [PATCH v3 7/8] mm/mempolicy: " js1304
2020-06-25 12:09 ` Michal Hocko
2020-07-03 15:59 ` Vlastimil Babka
2020-07-08 1:20 ` Qian Cai
2020-07-08 6:45 ` Michal Hocko
2020-10-08 3:21 ` Hugh Dickins
2020-10-08 17:29 ` Mike Kravetz
2020-10-09 5:50 ` Hugh Dickins
2020-10-09 17:42 ` Mike Kravetz
2020-10-09 22:23 ` Hugh Dickins
2020-10-10 0:25 ` Mike Kravetz
2020-06-23 6:13 ` [PATCH v3 8/8] mm/page_alloc: remove a wrapper for alloc_migration_target() js1304
2020-06-25 12:10 ` Michal Hocko
2020-07-03 16:18 ` Vlastimil Babka
2020-07-06 8:44 ` Joonsoo Kim
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