From: Michal Hocko <mhocko@kernel.org>
To: Joonsoo Kim <js1304@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@lge.com, Christoph Hellwig <hch@infradead.org>,
Roman Gushchin <guro@fb.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Subject: Re: [PATCH v4 04/11] mm/hugetlb: make hugetlb migration callback CMA aware
Date: Thu, 9 Jul 2020 08:43:40 +0200 [thread overview]
Message-ID: <20200709064340.GB19160@dhcp22.suse.cz> (raw)
In-Reply-To: <20200708074103.GD7271@dhcp22.suse.cz>
On Wed 08-07-20 09:41:06, Michal Hocko wrote:
> On Wed 08-07-20 16:16:02, Joonsoo Kim wrote:
> > On Tue, Jul 07, 2020 at 01:22:31PM +0200, Vlastimil Babka wrote:
> > > On 7/7/20 9:44 AM, js1304@gmail.com 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.
> > > >
> > > > hugetlb page allocation process consists of two steps. First is dequeing
> > > > from the pool. Second is, if there is no available page on the queue,
> > > > allocating from the page allocator.
> > > >
> > > > new_non_cma_page() can control allocation from the page allocator by
> > > > specifying correct gfp flag. However, dequeing cannot be controlled until
> > > > now, so, new_non_cma_page() skips dequeing completely. It is a suboptimal
> > > > since new_non_cma_page() cannot utilize hugetlb pages on the queue so this
> > > > patch tries to fix this situation.
> > > >
> > > > This patch makes the deque function on hugetlb CMA aware and skip CMA
> > > > pages if newly added skip_cma argument is passed as true.
> > >
> > > Hmm, can't you instead change dequeue_huge_page_node_exact() to test the PF_
> > > flag and avoid adding bool skip_cma everywhere?
> >
> > Okay! Please check following patch.
> > >
> > > I think that's what Michal suggested [1] except he said "the code already does
> > > by memalloc_nocma_{save,restore} API". It needs extending a bit though, AFAICS.
> > > __gup_longterm_locked() indeed does the save/restore, but restore comes before
> > > check_and_migrate_cma_pages() and thus new_non_cma_page() is called, so an
> > > adjustment is needed there, but that's all?
> > >
> > > Hm the adjustment should be also done because save/restore is done around
> > > __get_user_pages_locked(), but check_and_migrate_cma_pages() also calls
> > > __get_user_pages_locked(), and that call not being between nocma save and
> > > restore is thus also a correctness issue?
> >
> > Simply, I call memalloc_nocma_{save,restore} in new_non_cma_page(). It
> > would not cause any problem.
>
> I believe a proper fix is the following. The scope is really defined for
> FOLL_LONGTERM pins and pushing it inside check_and_migrate_cma_pages
> will solve the problem as well but it imho makes more sense to do it in
> the caller the same way we do for any others.
>
> Fixes: 9a4e9f3b2d73 ("mm: update get_user_pages_longterm to migrate pages allocated from CMA region")
>
> I am not sure this is worth backporting to stable yet.
Should I post it as a separate patch do you plan to include this into your next version?
>
> diff --git a/mm/gup.c b/mm/gup.c
> index de9e36262ccb..75980dd5a2fc 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1794,7 +1794,6 @@ static long __gup_longterm_locked(struct task_struct *tsk,
> vmas_tmp, NULL, gup_flags);
>
> if (gup_flags & FOLL_LONGTERM) {
> - memalloc_nocma_restore(flags);
> if (rc < 0)
> goto out;
>
> @@ -1802,11 +1801,13 @@ static long __gup_longterm_locked(struct task_struct *tsk,
> for (i = 0; i < rc; i++)
> put_page(pages[i]);
> rc = -EOPNOTSUPP;
> + memalloc_nocma_restore(flags);
> goto out;
> }
>
> rc = check_and_migrate_cma_pages(tsk, mm, start, rc, pages,
> vmas_tmp, gup_flags);
> + memalloc_nocma_restore(flags);
> }
>
> out:
> --
> Michal Hocko
> SUSE Labs
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-07-09 6:43 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 7:44 [PATCH v4 00/11] clean-up the migration target allocation functions js1304
2020-07-07 7:44 ` [PATCH v4 01/11] mm/page_isolation: prefer the node of the source page js1304
2020-07-07 7:44 ` [PATCH v4 02/11] mm/migrate: move migration helper from .h to .c js1304
2020-07-07 7:44 ` [PATCH v4 03/11] mm/hugetlb: unify migration callbacks js1304
2020-07-07 11:05 ` Vlastimil Babka
2020-07-07 11:19 ` Michal Hocko
2020-07-07 7:44 ` [PATCH v4 04/11] mm/hugetlb: make hugetlb migration callback CMA aware js1304
2020-07-07 11:22 ` Vlastimil Babka
2020-07-08 7:16 ` Joonsoo Kim
2020-07-08 7:41 ` Michal Hocko
2020-07-08 9:26 ` Vlastimil Babka
2020-07-08 10:57 ` Aneesh Kumar K.V
2020-07-08 11:32 ` Michal Hocko
2020-07-09 6:43 ` Michal Hocko [this message]
2020-07-09 7:03 ` Joonsoo Kim
2020-07-09 0:27 ` Mike Kravetz
2020-07-07 11:31 ` Michal Hocko
2020-07-08 6:48 ` Michal Hocko
2020-07-08 7:12 ` Joonsoo Kim
2020-07-07 7:44 ` [PATCH v4 05/11] mm/migrate: clear __GFP_RECLAIM for THP allocation for migration js1304
2020-07-07 11:40 ` Michal Hocko
2020-07-08 7:19 ` Joonsoo Kim
2020-07-08 7:48 ` Michal Hocko
2020-07-09 3:26 ` Joonsoo Kim
2020-07-07 12:17 ` Vlastimil Babka
2020-07-08 7:17 ` Joonsoo Kim
2020-07-09 7:17 ` Joonsoo Kim
2020-07-07 7:44 ` [PATCH v4 06/11] mm/migrate: make a standard migration target allocation function js1304
2020-07-07 11:43 ` Michal Hocko
2020-07-07 14:49 ` Vlastimil Babka
2020-07-07 19:00 ` Michal Hocko
2020-07-09 7:15 ` Joonsoo Kim
2020-07-09 10:28 ` Michal Hocko
2020-07-07 7:44 ` [PATCH v4 07/11] mm/gup: use a standard migration target allocation callback js1304
2020-07-07 11:46 ` Michal Hocko
2020-07-08 7:21 ` Joonsoo Kim
2020-07-07 7:44 ` [PATCH v4 08/11] mm/mempolicy: " js1304
2020-07-07 7:44 ` [PATCH v4 09/11] mm/page_alloc: remove a wrapper for alloc_migration_target() js1304
2020-07-07 7:44 ` [PATCH v4 10/11] mm/memory-failure: " js1304
2020-07-07 11:48 ` Michal Hocko
2020-07-07 15:03 ` Vlastimil Babka
2020-07-07 18:55 ` Michal Hocko
2020-07-07 15:00 ` Vlastimil Babka
2020-07-07 7:44 ` [PATCH v4 11/11] mm/memory_hotplug: " js1304
2020-07-07 11:52 ` Michal Hocko
2020-07-07 15:09 ` Vlastimil Babka
2020-07-09 3:25 ` Joonsoo Kim
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