Groups > linux.kernel > #1632033

Re: Freeing HugeTLB page into buddy allocator

From	Anshuman Khandual <khandual@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: Freeing HugeTLB page into buddy allocator
Date	2017-04-27 13:20 +0200
Message-ID	<tAPCN-8aG-3@gated-at.bofh.it> (permalink)
References	<tA4ud-2ow-9@gated-at.bofh.it> <tAKD8-4DF-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

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.

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Freeing HugeTLB page into buddy allocator Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-04-25 11:00 +0200
  Re: Freeing HugeTLB page into buddy allocator Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> - 2017-04-27 08:00 +0200
    Re: Freeing HugeTLB page into buddy allocator Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-04-27 13:20 +0200

csiph-web