From: Mike Kravetz <mike.kravetz@oracle.com>
To: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Muchun Song <songmuchun@bytedance.com>,
David Hildenbrand <david@redhat.com>,
Oscar Salvador <osalvador@suse.de>,
Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v2 2/5] hugetlb: convert page_huge_active() HPageMigratable flag
Date: Fri, 22 Jan 2021 15:12:19 -0800 [thread overview]
Message-ID: <634f94d9-5d81-f7a3-4201-53d48e4a9a27@oracle.com> (raw)
In-Reply-To: <0159cbc4-6d98-fefe-2288-5ba28b3f519f@huawei.com>
On 1/21/21 10:53 PM, Miaohe Lin wrote:
> Hi:
> On 2021/1/20 9:30, Mike Kravetz wrote:
>> Use the new hugetlb page specific flag HPageMigratable to replace the
>> page_huge_active interfaces. By it's name, page_huge_active implied
>> that a huge page was on the active list. However, that is not really
>> what code checking the flag wanted to know. It really wanted to determine
>> if the huge page could be migrated. This happens when the page is actually
>> added the page cache and/or task page table. This is the reasoning behind
>
> s/added/added to/
Thanks
>
>> the name change.
>>
...
>> @@ -1260,7 +1260,13 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
>> if (!PageHuge(page))
>> continue;
>> head = compound_head(page);
>> - if (page_huge_active(head))
>> + /*
>> + * This test is racy as we hold no reference or lock. The
>> + * hugetlb page could have been free'ed and head is no longer
>> + * a hugetlb page before the following check. In such unlikely
>> + * cases false positives and negatives are possible.
>> + */
>
> Is it necessary to mention that: "offline_pages() could handle these racy cases." in the comment ?
>
I will enhance the comment to say that calling code must deal with these
possible scenarios.
--
Mike Kravetz
>> + if (HPageMigratable(head))
>> goto found;
>> skip = compound_nr(head) - (page - head);
>> pfn += skip - 1;
>>
>
> Looks good to me. Thanks.
>
> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
>
next prev parent reply other threads:[~2021-01-22 23:12 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-20 1:30 [PATCH v2 0/5] create hugetlb flags to consolidate state Mike Kravetz
2021-01-20 1:30 ` [PATCH v2 1/5] hugetlb: use page.private for hugetlb specific page flags Mike Kravetz
2021-01-20 8:10 ` Miaohe Lin
2021-01-20 8:43 ` kernel test robot
2021-01-20 9:30 ` Oscar Salvador
2021-01-20 18:12 ` Mike Kravetz
2021-01-20 1:30 ` [PATCH v2 2/5] hugetlb: convert page_huge_active() HPageMigratable flag Mike Kravetz
2021-01-20 9:59 ` Oscar Salvador
2021-01-20 10:00 ` Oscar Salvador
2021-01-20 21:48 ` Mike Kravetz
2021-01-21 8:18 ` Oscar Salvador
2021-01-21 8:27 ` Oscar Salvador
2021-01-21 12:01 ` [External] " Muchun Song
2021-01-22 6:53 ` Miaohe Lin
2021-01-22 23:12 ` Mike Kravetz [this message]
2021-02-03 7:42 ` [External] " Muchun Song
2021-02-04 0:44 ` Mike Kravetz
2021-01-20 1:30 ` [PATCH v2 3/5] hugetlb: only set HPageMigratable for migratable hstates Mike Kravetz
2021-01-20 1:30 ` [PATCH v2 4/5] hugetlb: convert PageHugeTemporary() to HPageTemporary flag Mike Kravetz
2021-01-20 10:09 ` Oscar Salvador
2021-01-20 18:14 ` Mike Kravetz
2021-01-20 1:30 ` [PATCH v2 5/5] hugetlb: convert PageHugeFreed to HPageFreed flag Mike Kravetz
2021-01-20 10:10 ` Oscar Salvador
2021-01-20 10:44 ` [External] " Muchun Song
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