From: Mike Kravetz <mike.kravetz@oracle.com>
To: ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: 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>,
Vlastimil Babka <vbabka@suse.cz>,
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 00/31] Generating physically contiguous memory after page allocation
Date: Tue, 19 Feb 2019 17:42:14 -0800 [thread overview]
Message-ID: <f4cf53a3-359b-8c66-ed15-112b3cf0f475@oracle.com> (raw)
In-Reply-To: <20190215220856.29749-1-zi.yan@sent.com>
On 2/15/19 2:08 PM, Zi Yan wrote:
Thanks for working on this issue!
I have not yet had a chance to take a look at the code. However, I do have
some general questions/comments on the approach.
> Patch structure
> ----
>
> The patchset I developed to generate physically contiguous memory/arbitrary
> sized pages merely moves pages around. There are three components in this
> patchset:
>
> 1) a new page migration mechanism, called exchange pages, that exchanges the
> content of two in-use pages instead of performing two back-to-back page
> migration. It saves on overheads and avoids page reclaim and memory compaction
> in the page allocation path, although it is not strictly required if enough
> free memory is available in the system.
>
> 2) a new mechanism that utilizes both page migration and exchange pages to
> produce physically contiguous memory/arbitrary sized pages without allocating
> any new pages, unlike what khugepaged does. It works on per-VMA basis, creating
> physically contiguous memory out of each VMA, which is virtually contiguous.
> A simple range tree is used to ensure no two VMAs are overlapping with each
> other in the physical address space.
This appears to be a new approach to generating contiguous areas. Previous
attempts had relied on finding a contiguous area that can then be used for
various purposes including user mappings. Here, you take an existing mapping
and make it contiguous. [RFC PATCH 04/31] mm: add mem_defrag functionality
talks about creating a (VPN, PFN) anchor pair for each vma and then using
this pair as the base for creating a contiguous area.
I'm curious, how 'fixed' is the anchor? As you know, there could be a
non-movable page in the PFN range. As a result, you will not be able to
create a contiguous area starting at that PFN. In such a case, do we try
another PFN? I know this could result in much page shuffling. I'm just
trying to figure out how we satisfy a user who really wants a contiguous
area. Is there some method to keep trying?
My apologies if this is addressed in the code. This was just one of the
first thoughts that came to mine when giving the series a quick look.
--
Mike Kravetz
next prev parent reply other threads:[~2019-02-20 1:42 UTC|newest]
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
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 ` Mike Kravetz [this message]
2019-02-20 2:33 ` [RFC PATCH 00/31] Generating physically contiguous memory after page allocation 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
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