From: Miaohe Lin <linmiaohe@huawei.com>
To: Mike Kravetz <mike.kravetz@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: <songmuchun@bytedance.com>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/6] mm/hugetlb: fix incorrect update of max_huge_pages
Date: Wed, 17 Aug 2022 09:53:47 +0800 [thread overview]
Message-ID: <5eebaeff-c002-2a1e-b5bb-fffe7e987ca0@huawei.com> (raw)
In-Reply-To: <Yvwpl/RD9tLr6HJE@monkey>
On 2022/8/17 7:34, Mike Kravetz wrote:
> On 08/16/22 16:20, Andrew Morton wrote:
>> On Tue, 16 Aug 2022 15:52:47 -0700 Mike Kravetz <mike.kravetz@oracle.com> wrote:
>>
>>> On 08/16/22 21:05, Miaohe Lin wrote:
>>>> There should be pages_per_huge_page(h) / pages_per_huge_page(target_hstate)
>>>> pages incremented for target_hstate->max_huge_pages when page is demoted.
>>>> Update max_huge_pages accordingly for consistency.
>>>>
>>>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>>>> ---
>>>> mm/hugetlb.c | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>>> index ea1c7bfa1cc3..e72052964fb5 100644
>>>> --- a/mm/hugetlb.c
>>>> +++ b/mm/hugetlb.c
>>>> @@ -3472,7 +3472,8 @@ static int demote_free_huge_page(struct hstate *h, struct page *page)
>>>> * based on pool changes for the demoted page.
>>>> */
>>>> h->max_huge_pages--;
>>>> - target_hstate->max_huge_pages += pages_per_huge_page(h);
>>>> + target_hstate->max_huge_pages +=
>>>> + pages_per_huge_page(h) / pages_per_huge_page(target_hstate);
>>>
>>> Thanks!
>>>
>>> That is indeed incorrect. However the miscalculation should not have any
>>> consequences. Correct? The value is used when initially populating the
>>> pools. It is never read and used again. It is written to in
>>> set_max_huge_pages if someone changes the number of hugetlb pages.
>>>
>>> I guess that is a long way of saying I am not sure why we care about trying
>>> to keep max_huge_pages up to date? I do not think it matters.
>>>
>>> I also thought, if we are going to adjust max_huge_pages here we may
>>> also want to adjust the node specific value: h->max_huge_pages_node[node].
>>> There are a few other places where the global max_huge_pages is adjusted
>>> without adjusting the node specific value.
>>>
>>> The more I think about it, the more I think we should explore just
>>> eliminating any adjustment of this/these values after initially
>>> populating the pools.
>>
>> I'm thinking we should fix something that is "indeed incorrect" before
>> going on to more extensive things?
>
> Sure, I am good with that.
>
> Just wanted to point out that the incorrect calculation does not have
> any negative consequences. Maybe prompting Miaohe to look into the more
> extensive cleanup.
Many thanks both. I will try to do this "more extensive cleanup" after pending work is done.
Thanks,
Miaohe Lin
next prev parent reply other threads:[~2022-08-17 1:53 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-16 13:05 [PATCH 0/6] A few fixup patches for hugetlb Miaohe Lin
2022-08-16 13:05 ` [PATCH 1/6] mm/hugetlb: fix incorrect update of max_huge_pages Miaohe Lin
2022-08-16 22:52 ` Mike Kravetz
2022-08-16 23:20 ` Andrew Morton
2022-08-16 23:34 ` Mike Kravetz
2022-08-17 1:53 ` Miaohe Lin [this message]
2022-08-17 2:28 ` Muchun Song
2022-08-16 13:05 ` [PATCH 2/6] mm/hugetlb: fix WARN_ON(!kobj) in sysfs_create_group() Miaohe Lin
2022-08-16 22:55 ` Mike Kravetz
2022-08-17 2:31 ` Muchun Song
2022-08-17 2:39 ` Miaohe Lin
2022-08-16 13:05 ` [PATCH 3/6] mm/hugetlb: fix missing call to restore_reserve_on_error() Miaohe Lin
2022-08-16 23:31 ` Mike Kravetz
2022-08-17 1:59 ` Miaohe Lin
2022-08-16 13:05 ` [PATCH 4/6] mm: hugetlb_vmemmap: add missing smp_wmb() before set_pte_at() Miaohe Lin
2022-08-17 2:53 ` Muchun Song
2022-08-17 8:41 ` Miaohe Lin
2022-08-17 9:13 ` Yin, Fengwei
2022-08-17 11:21 ` Muchun Song
2022-08-18 1:14 ` Yin, Fengwei
2022-08-18 1:55 ` Miaohe Lin
2022-08-18 2:00 ` Yin, Fengwei
2022-08-18 2:47 ` Muchun Song
2022-08-18 7:52 ` Miaohe Lin
2022-08-18 7:59 ` Muchun Song
2022-08-18 8:32 ` Yin, Fengwei
2022-08-18 8:40 ` Muchun Song
2022-08-18 8:54 ` Yin, Fengwei
2022-08-18 9:18 ` Muchun Song
2022-08-18 12:58 ` Miaohe Lin
2022-08-18 23:53 ` Yin, Fengwei
2022-08-19 3:19 ` Muchun Song
2022-08-19 7:26 ` Miaohe Lin
2022-08-18 1:15 ` Yin, Fengwei
2022-08-20 8:12 ` Muchun Song
2022-08-22 8:45 ` Miaohe Lin
2022-08-22 10:23 ` Muchun Song
2022-08-23 1:42 ` Miaohe Lin
2022-08-16 13:05 ` [PATCH 5/6] mm/hugetlb: fix sysfs group leak in hugetlb_unregister_node() Miaohe Lin
2022-08-17 9:41 ` Yin, Fengwei
2022-08-18 1:00 ` Yin, Fengwei
2022-08-18 1:12 ` Yin, Fengwei
2022-08-16 13:05 ` [PATCH 6/6] mm/hugetlb: make detecting shared pte more reliable Miaohe Lin
2022-08-17 23:56 ` Mike Kravetz
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