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From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Zi Yan <ziy@nvidia.com>, Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Michal Hocko <mhocko@kernel.org>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	John Hubbard <jhubbard@nvidia.com>,
	Mark Hairgrove <mhairgrove@nvidia.com>,
	Nitin Gupta <nigupta@nvidia.com>,
	David Nellans <dnellans@nvidia.com>
Subject: Re: [RFC PATCH 01/31] mm: migrate: Add exchange_pages to exchange two lists of pages.
Date: Tue, 19 Feb 2019 13:12:07 +0530
Message-ID: <1ce6ae99-4865-df62-5f20-cb07ebb95327@arm.com> (raw)
In-Reply-To: <C84D2490-B6C6-4C7C-870F-945E31719728@nvidia.com>



On 02/18/2019 11:29 PM, Zi Yan wrote:
> On 18 Feb 2019, at 9:52, Matthew Wilcox wrote:
> 
>> On Mon, Feb 18, 2019 at 09:51:33AM -0800, Zi Yan wrote:
>>> On 18 Feb 2019, at 9:42, Vlastimil Babka wrote:
>>>> On 2/18/19 6:31 PM, Zi Yan wrote:
>>>>> The purpose of proposing exchange_pages() is to avoid allocating any
>>>>> new
>>>>> page,
>>>>> so that we would not trigger any potential page reclaim or memory
>>>>> compaction.
>>>>> Allocating a temporary page defeats the purpose.
>>>>
>>>> Compaction can only happen for order > 0 temporary pages. Even if you
>>>> used
>>>> single order = 0 page to gradually exchange e.g. a THP, it should be
>>>> better than
>>>> u64. Allocating order = 0 should be a non-issue. If it's an issue, then
>>>> the
>>>> system is in a bad state and physically contiguous layout is a secondary
>>>> concern.
>>>
>>> You are right if we only need to allocate one order-0 page. But this also
>>> means
>>> we can only exchange two pages at a time. We need to add a lock to make sure
>>> the temporary page is used exclusively or we need to keep allocating
>>> temporary pages
>>> when multiple exchange_pages() are happening at the same time.
>>
>> You allocate one temporary page per thread that's doing an exchange_page().
> 
> Yeah, you are right. I think at most I need NR_CPU order-0 pages. I will try
> it. Thanks.

But the location of this temp page matters as well because you would like to
saturate the inter node interface. It needs to be either of the nodes where
the source or destination page belongs. Any other node would generate two
internode copy process which is not what you intend here I guess.


  reply index

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-15 22:08 [RFC PATCH 00/31] Generating physically contiguous memory after page allocation Zi Yan
2019-02-15 22:08 ` [RFC PATCH 01/31] mm: migrate: Add exchange_pages to exchange two lists of pages Zi Yan
2019-02-17 11:29   ` Matthew Wilcox
2019-02-18 17:31     ` Zi Yan
2019-02-18 17:42       ` Vlastimil Babka
2019-02-18 17:51         ` Zi Yan
2019-02-18 17:52           ` Matthew Wilcox
2019-02-18 17:59             ` Zi Yan
2019-02-19  7:42               ` Anshuman Khandual [this message]
2019-02-19 12:56                 ` Matthew Wilcox
2019-02-20  4:38                   ` Anshuman Khandual
2019-03-14  2:39                     ` Zi Yan
2019-02-21 21:10   ` Jerome Glisse
2019-02-21 21:25     ` Zi Yan
2019-02-15 22:08 ` [RFC PATCH 02/31] mm: migrate: Add THP exchange support Zi Yan
2019-02-15 22:08 ` [RFC PATCH 03/31] mm: migrate: Add tmpfs " Zi Yan
2019-02-15 22:08 ` [RFC PATCH 04/31] mm: add mem_defrag functionality Zi Yan
2019-02-15 22:08 ` [RFC PATCH 05/31] mem_defrag: split a THP if either src or dst is THP only Zi Yan
2019-02-15 22:08 ` [RFC PATCH 06/31] mm: Make MAX_ORDER configurable in Kconfig for buddy allocator Zi Yan
2019-02-15 22:08 ` [RFC PATCH 07/31] mm: deallocate pages with order > MAX_ORDER Zi Yan
2019-02-15 22:08 ` [RFC PATCH 08/31] mm: add pagechain container for storing multiple pages Zi Yan
2019-02-15 22:08 ` [RFC PATCH 09/31] mm: thp: 1GB anonymous page implementation Zi Yan
2019-02-15 22:08 ` [RFC PATCH 10/31] mm: proc: add 1GB THP kpageflag Zi Yan
2019-02-15 22:08 ` [RFC PATCH 11/31] mm: debug: print compound page order in dump_page() Zi Yan
2019-02-15 22:08 ` [RFC PATCH 12/31] mm: stats: Separate PMD THP and PUD THP stats Zi Yan
2019-02-15 22:08 ` [RFC PATCH 13/31] mm: thp: 1GB THP copy on write implementation Zi Yan
2019-02-15 22:08 ` [RFC PATCH 14/31] mm: thp: handling 1GB THP reference bit Zi Yan
2019-02-15 22:08 ` [RFC PATCH 15/31] mm: thp: add 1GB THP split_huge_pud_page() function Zi Yan
2019-02-15 22:08 ` [RFC PATCH 16/31] mm: thp: check compound_mapcount of PMD-mapped PUD THPs at free time Zi Yan
2019-02-15 22:08 ` [RFC PATCH 17/31] mm: thp: split properly PMD-mapped PUD THP to PTE-mapped PUD THP Zi Yan
2019-02-15 22:08 ` [RFC PATCH 18/31] mm: page_vma_walk: teach it about PMD-mapped " Zi Yan
2019-02-15 22:08 ` [RFC PATCH 19/31] mm: thp: 1GB THP support in try_to_unmap() Zi Yan
2019-02-15 22:08 ` [RFC PATCH 20/31] mm: thp: split 1GB THPs at page reclaim Zi Yan
2019-02-15 22:08 ` [RFC PATCH 21/31] mm: thp: 1GB zero page shrinker Zi Yan
2019-02-15 22:08 ` [RFC PATCH 22/31] mm: thp: 1GB THP follow_p*d_page() support Zi Yan
2019-02-15 22:08 ` [RFC PATCH 23/31] mm: support 1GB THP pagemap support Zi Yan
2019-02-15 22:08 ` [RFC PATCH 24/31] sysctl: add an option to only print the head page virtual address Zi Yan
2019-02-15 22:08 ` [RFC PATCH 25/31] mm: thp: add a knob to enable/disable 1GB THPs Zi Yan
2019-02-15 22:08 ` [RFC PATCH 26/31] mm: thp: promote PTE-mapped THP to PMD-mapped THP Zi Yan
2019-02-15 22:08 ` [RFC PATCH 27/31] mm: thp: promote PMD-mapped PUD pages to PUD-mapped PUD pages Zi Yan
2019-02-15 22:08 ` [RFC PATCH 28/31] mm: vmstats: add page promotion stats Zi Yan
2019-02-15 22:08 ` [RFC PATCH 29/31] mm: madvise: add madvise options to split PMD and PUD THPs Zi Yan
2019-02-15 22:08 ` [RFC PATCH 30/31] mm: mem_defrag: thp: PMD THP and PUD THP in-place promotion support Zi Yan
2019-02-15 22:08 ` [RFC PATCH 31/31] sysctl: toggle to promote PUD-mapped 1GB THP or not Zi Yan
2019-02-20  1:42 ` [RFC PATCH 00/31] Generating physically contiguous memory after page allocation Mike Kravetz
2019-02-20  2:33   ` Zi Yan
2019-02-20  3:18     ` Mike Kravetz
2019-02-20  5:19       ` Zi Yan
2019-02-20  5:27         ` Mike Kravetz
  -- strict thread matches above, loose matches on Subject: below --
2019-02-15 22:03 Zi Yan
2019-02-15 22:03 ` [RFC PATCH 01/31] mm: migrate: Add exchange_pages to exchange two lists of pages Zi Yan

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