From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
To: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: "wujianguo@huawei.com" <wujianguo@huawei.com>,
Linux Memory Management List <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Freeing HugeTLB page into buddy allocator
Date: Thu, 27 Apr 2017 16:36:20 +0530 [thread overview]
Message-ID: <d40857d7-3162-cf83-dd0e-313555414f5b@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170427055457.GA19344@hori1.linux.bs1.fc.nec.co.jp>
On 04/27/2017 11:24 AM, Naoya Horiguchi wrote:
> On Tue, Apr 25, 2017 at 02:27:27PM +0530, Anshuman Khandual wrote:
>> Hello Jianguo,
>>
>> In the commit a49ecbcd7b0d5a1cda, it talks about HugeTLB page being
>> freed into buddy allocator instead of hugepage_freelists. But if
>> I look the code closely for the function unmap_and_move_huge_page()
>> it only calls putback_active_hugepage() which puts the page into the
>> huge page active list to free up the source HugeTLB page after any
>> successful migration. I might be missing something here, so can you
>> please point me where we release the HugeTLB page into buddy allocator
>> directly during migration ?
>
> Hi Anshuman,
>
> As stated in the patch description, source hugetlb page is freed after
> successful migration if overcommit is configured.
>
> The call chain is like below:
>
> soft_offline_huge_page
> migrate_pages
> unmap_and_move_huge_page
> putback_active_hugepage(hpage)
> put_page // refcount is down to 0
> __put_page
> __put_compound_page
> free_huge_page
> if (h->surplus_huge_pages_node[nid])
> update_and_free_page
> __free_pages
>
> So the inline comment
>
> + /* overcommit hugetlb page will be freed to buddy */
>
> might be confusing because at this point the overcommit hugetlb page was
> already freed to buddy.
>
> I hope this will help you.
Surely does. Thanks Naoya.
prev parent reply other threads:[~2017-04-27 11:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-25 8:57 Freeing HugeTLB page into buddy allocator Anshuman Khandual
2017-04-27 5:54 ` Naoya Horiguchi
2017-04-27 11:06 ` Anshuman Khandual [this message]
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