From: "HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>
To: Miaohe Lin <linmiaohe@huawei.com>,
Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Liu Shixin <liushixin2@huawei.com>,
Yang Shi <shy828301@gmail.com>,
Oscar Salvador <osalvador@suse.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH v2 1/9] mm/hugetlb: remove checking hstate_is_gigantic() in return_unused_surplus_pages()
Date: Fri, 24 Jun 2022 08:34:42 +0000 [thread overview]
Message-ID: <20220624083428.GA2070418@hori.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <e9a22524-d9f6-1018-a712-00adb90d432a@huawei.com>
On Fri, Jun 24, 2022 at 04:15:19PM +0800, Miaohe Lin wrote:
> On 2022/6/24 16:03, Muchun Song wrote:
> > On Fri, Jun 24, 2022 at 10:25:48AM +0800, Miaohe Lin wrote:
> >> On 2022/6/24 7:51, Naoya Horiguchi wrote:
> >>> From: Naoya Horiguchi <naoya.horiguchi@nec.com>
> >>>
> >>> I found a weird state of 1GB hugepage pool, caused by the following
> >>> procedure:
> >>>
> >>> - run a process reserving all free 1GB hugepages,
> >>> - shrink free 1GB hugepage pool to zero (i.e. writing 0 to
> >>> /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages), then
> >>> - kill the reserving process.
> >>>
> >>> , then all the hugepages are free *and* surplus at the same time.
> >>>
> >>> $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
> >>> 3
> >>> $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/free_hugepages
> >>> 3
> >>> $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/resv_hugepages
> >>> 0
> >>> $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/surplus_hugepages
> >>> 3
> >>>
> >>> This state is resolved by reserving and allocating the pages then
> >>> freeing them again, so this seems not to result in serious problem.
> >>> But it's a little surprizing (shrinking pool suddenly fails).
> >>>
> >>> This behavior is caused by hstate_is_gigantic() check in
> >>> return_unused_surplus_pages(). This was introduced so long ago in 2008
> >>> by commit aa888a74977a ("hugetlb: support larger than MAX_ORDER"), and
> >>> it seems to me that this check is no longer unnecessary. Let's remove it.
> >>
> >> s/unnecessary/necessary/
Thanks, I fixed it.
> >>
> >>>
> >>> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
> >>> ---
> >>> mm/hugetlb.c | 4 ----
> >>> 1 file changed, 4 deletions(-)
> >>>
> >>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> >>> index a57e1be41401..c538278170a2 100644
> >>> --- a/mm/hugetlb.c
> >>> +++ b/mm/hugetlb.c
> >>> @@ -2432,10 +2432,6 @@ static void return_unused_surplus_pages(struct hstate *h,
> >>> /* Uncommit the reservation */
> >>> h->resv_huge_pages -= unused_resv_pages;
> >>>
> >>> - /* Cannot return gigantic pages currently */
> >>> - if (hstate_is_gigantic(h))
> >>> - goto out;
> >>> -
> >>
> >> IIUC it might be better to do the below check:
> >> /*
> >> * Cannot return gigantic pages currently if runtime gigantic page
> >> * allocation is not supported.
> >> */
> >> if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
> >> goto out;
> >>
> >
> > The change looks good to me. However, the comments above is unnecessary
> > since gigantic_page_runtime_supported() is straightforward.
>
> Agree. The comments can be removed.
Thank you, both. Adding !gigantic_page_runtime_supported without comment
makes sense to me.
Thanks,
Naoya Horiguchi
next prev parent reply other threads:[~2022-06-24 8:34 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-23 23:51 [PATCH v2 0/9] mm, hwpoison: enable 1GB hugepage support (v2) Naoya Horiguchi
2022-06-23 23:51 ` [PATCH v2 1/9] mm/hugetlb: remove checking hstate_is_gigantic() in return_unused_surplus_pages() Naoya Horiguchi
2022-06-24 2:25 ` Miaohe Lin
2022-06-24 8:03 ` Muchun Song
2022-06-24 8:15 ` Miaohe Lin
2022-06-24 8:34 ` HORIGUCHI NAOYA(堀口 直也) [this message]
2022-06-24 19:11 ` Mike Kravetz
2022-06-27 6:02 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-27 17:25 ` Mike Kravetz
2022-06-28 3:01 ` Miaohe Lin
2022-06-28 8:38 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-30 2:27 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-23 23:51 ` [PATCH v2 2/9] mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page_range() Naoya Horiguchi
2022-06-24 9:23 ` Miaohe Lin
2022-06-27 6:06 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-24 20:57 ` Mike Kravetz
2022-06-27 6:48 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-27 7:57 ` Muchun Song
2022-06-23 23:51 ` [PATCH v2 3/9] mm/hugetlb: make pud_huge() and huge_pud() aware of non-present pud entry Naoya Horiguchi
2022-06-24 8:40 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-25 0:02 ` Mike Kravetz
2022-06-27 7:07 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-25 9:42 ` Miaohe Lin
2022-06-27 7:24 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-23 23:51 ` [PATCH v2 4/9] mm, hwpoison, hugetlb: support saving mechanism of raw error pages Naoya Horiguchi
2022-06-27 3:16 ` Miaohe Lin
2022-06-27 7:56 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-27 9:26 ` Muchun Song
2022-06-28 2:41 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-28 6:26 ` Muchun Song
2022-06-28 7:51 ` Muchun Song
2022-06-28 8:17 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-28 10:37 ` Muchun Song
2022-06-23 23:51 ` [PATCH v2 5/9] mm, hwpoison: make unpoison aware of raw error info in hwpoisoned hugepage Naoya Horiguchi
2022-06-27 8:32 ` Miaohe Lin
2022-06-27 11:48 ` Miaohe Lin
2022-06-23 23:51 ` [PATCH v2 6/9] mm, hwpoison: set PG_hwpoison for busy hugetlb pages Naoya Horiguchi
2022-06-27 8:39 ` Miaohe Lin
2022-06-23 23:51 ` [PATCH v2 7/9] mm, hwpoison: make __page_handle_poison returns int Naoya Horiguchi
2022-06-27 9:02 ` Miaohe Lin
2022-06-28 6:02 ` HORIGUCHI NAOYA(堀口 直也)
2022-06-23 23:51 ` [PATCH v2 8/9] mm, hwpoison: skip raw hwpoison page in freeing 1GB hugepage Naoya Horiguchi
2022-06-27 12:24 ` Miaohe Lin
2022-06-23 23:51 ` [PATCH v2 9/9] mm, hwpoison: enable memory error handling on " Naoya Horiguchi
2022-06-28 2:06 ` Miaohe Lin
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