From: David Hildenbrand <david@redhat.com>
To: Muchun Song <songmuchun@bytedance.com>,
mike.kravetz@oracle.com, akpm@linux-foundation.org
Cc: n-horiguchi@ah.jp.nec.com, ak@linux.intel.com, mhocko@suse.cz,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Yang Shi <shy828301@gmail.com>, Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH v4 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one
Date: Wed, 13 Jan 2021 11:30:31 +0100 [thread overview]
Message-ID: <82b0f54d-4138-ee72-4c57-27fda40e0f98@redhat.com> (raw)
In-Reply-To: <20210113052209.75531-2-songmuchun@bytedance.com>
On 13.01.21 06:22, Muchun Song wrote:
> All pages isolated for the migration have an elevated reference count
> and therefore seeing a reference count equal to 1 means that the last
> user of the page has dropped the reference and the page has became
> unused and there doesn't make much sense to migrate it anymore. This has
> been done for regular pages and this patch does the same for hugetlb
> pages. Although the likelyhood of the race is rather small for hugetlb
> pages it makes sense the two code paths in sync.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> Acked-by: Yang Shi <shy828301@gmail.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/migrate.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 4385f2fb5d18..a6631c4eb6a6 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
> return -ENOSYS;
> }
>
> + if (page_count(hpage) == 1) {
> + /* page was freed from under us. So we are done. */
> + putback_active_hugepage(hpage);
> + return MIGRATEPAGE_SUCCESS;
> + }
> +
> new_hpage = get_new_page(hpage, private);
> if (!new_hpage)
> return -ENOMEM;
>
Happy to say that I now know understand what's going on here
Reviewed-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-01-13 10:32 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 5:22 [PATCH v4 0/6] Fix some bugs about HugeTLB code Muchun Song
2021-01-13 5:22 ` [PATCH v4 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one Muchun Song
2021-01-13 10:30 ` David Hildenbrand [this message]
2021-01-13 10:57 ` Oscar Salvador
2021-01-13 11:03 ` [External] " Muchun Song
2021-01-13 5:22 ` [PATCH v4 2/6] mm: hugetlbfs: fix cannot migrate the fallocated HugeTLB page Muchun Song
2021-01-13 11:00 ` Oscar Salvador
2021-01-13 5:22 ` [PATCH v4 3/6] mm: hugetlb: fix a race between freeing and dissolving the page Muchun Song
2021-01-13 9:31 ` Michal Hocko
2021-01-13 5:22 ` [PATCH v4 4/6] mm: hugetlb: retry dissolve page when hitting race Muchun Song
2021-01-13 9:33 ` Michal Hocko
2021-01-13 10:14 ` [External] " Muchun Song
2021-01-13 10:38 ` Michal Hocko
2021-01-13 11:11 ` Muchun Song
2021-01-13 11:14 ` Oscar Salvador
2021-01-13 11:20 ` Muchun Song
2021-01-13 12:03 ` Michal Hocko
2021-01-13 11:22 ` Michal Hocko
2021-01-13 12:15 ` Muchun Song
2021-01-13 5:22 ` [PATCH v4 5/6] mm: hugetlb: fix a race between isolating and freeing page Muchun Song
2021-01-13 5:22 ` [PATCH v4 6/6] mm: hugetlb: remove VM_BUG_ON_PAGE from page_huge_active Muchun Song
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=82b0f54d-4138-ee72-4c57-27fda40e0f98@redhat.com \
--to=david@redhat.com \
--cc=ak@linux.intel.com \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=mhocko@suse.cz \
--cc=mike.kravetz@oracle.com \
--cc=n-horiguchi@ah.jp.nec.com \
--cc=shy828301@gmail.com \
--cc=songmuchun@bytedance.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).