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From: Jason Gunthorpe <jgg@ziepe.ca>
To: Zi Yan <ziy@nvidia.com>
Cc: linux-mm@kvack.org, Roman Gushchin <guro@fb.com>,
	Rik van Riel <riel@surriel.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Matthew Wilcox <willy@infradead.org>,
	Shakeel Butt <shakeelb@google.com>,
	Yang Shi <yang.shi@linux.alibaba.com>,
	David Nellans <dnellans@nvidia.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 00/16] 1GB THP support on x86_64
Date: Wed, 2 Sep 2020 16:57:39 -0300	[thread overview]
Message-ID: <20200902195739.GI24045@ziepe.ca> (raw)
In-Reply-To: <C5EFA1CC-311C-47D5-9506-D087D9AE58D1@nvidia.com>

On Wed, Sep 02, 2020 at 03:05:39PM -0400, Zi Yan wrote:
> On 2 Sep 2020, at 14:48, Jason Gunthorpe wrote:
> 
> > On Wed, Sep 02, 2020 at 02:45:37PM -0400, Zi Yan wrote:
> >
> >>> Surprised this doesn't touch mm/pagewalk.c ?
> >>
> >> 1GB PUD page support is present for DAX purpose, so the code is there
> >> in mm/pagewalk.c already. I only needed to supply ops->pud_entry when using
> >> the functions in mm/pagewalk.c. :)
> >
> > Yes, but doesn't this change what is possible under the mmap_sem
> > without the page table locks?
> >
> > ie I would expect some thing like pmd_trans_unstable() to be required
> > as well for lockless walkers. (and I don't think the pmd code is 100%
> > right either)
> >
> 
> Right. I missed that. Thanks for pointing it out.
> The code like this, right?

Technically all those *pud's are racy too, the design here with the
_unstable function call always seemed weird. I strongly suspect it
should mirror how get_user_pages_fast works for lockless walking

Jason


  reply	other threads:[~2020-09-02 19:57 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-02 18:06 [RFC PATCH 00/16] 1GB THP support on x86_64 Zi Yan
2020-09-02 18:06 ` [RFC PATCH 01/16] mm: add pagechain container for storing multiple pages Zi Yan
2020-09-02 20:29   ` Randy Dunlap
2020-09-02 20:48     ` Zi Yan
2020-09-03  3:15   ` Matthew Wilcox
2020-09-07 12:22   ` Kirill A. Shutemov
2020-09-07 15:11     ` Zi Yan
2020-09-09 13:46       ` Kirill A. Shutemov
2020-09-09 14:15         ` Zi Yan
2020-09-02 18:06 ` [RFC PATCH 02/16] mm: thp: 1GB anonymous page implementation Zi Yan
2020-09-02 18:06 ` [RFC PATCH 03/16] mm: proc: add 1GB THP kpageflag Zi Yan
2020-09-09 13:46   ` Kirill A. Shutemov
2020-09-02 18:06 ` [RFC PATCH 04/16] mm: thp: 1GB THP copy on write implementation Zi Yan
2020-09-02 18:06 ` [RFC PATCH 05/16] mm: thp: handling 1GB THP reference bit Zi Yan
2020-09-09 14:09   ` Kirill A. Shutemov
2020-09-09 14:36     ` Zi Yan
2020-09-02 18:06 ` [RFC PATCH 06/16] mm: thp: add 1GB THP split_huge_pud_page() function Zi Yan
2020-09-09 14:18   ` Kirill A. Shutemov
2020-09-09 14:19     ` Zi Yan
2020-09-02 18:06 ` [RFC PATCH 07/16] mm: stats: make smap stats understand PUD THPs Zi Yan
2020-09-02 18:06 ` [RFC PATCH 08/16] mm: page_vma_walk: teach it about PMD-mapped PUD THP Zi Yan
2020-09-02 18:06 ` [RFC PATCH 09/16] mm: thp: 1GB THP support in try_to_unmap() Zi Yan
2020-09-02 18:06 ` [RFC PATCH 10/16] mm: thp: split 1GB THPs at page reclaim Zi Yan
2020-09-02 18:06 ` [RFC PATCH 11/16] mm: thp: 1GB THP follow_p*d_page() support Zi Yan
2020-09-02 18:06 ` [RFC PATCH 12/16] mm: support 1GB THP pagemap support Zi Yan
2020-09-02 18:06 ` [RFC PATCH 13/16] mm: thp: add a knob to enable/disable 1GB THPs Zi Yan
2020-09-02 18:06 ` [RFC PATCH 14/16] mm: page_alloc: >=MAX_ORDER pages allocation an deallocation Zi Yan
2020-09-02 18:06 ` [RFC PATCH 15/16] hugetlb: cma: move cma reserve function to cma.c Zi Yan
2020-09-02 18:06 ` [RFC PATCH 16/16] mm: thp: use cma reservation for pud thp allocation Zi Yan
2020-09-02 18:40 ` [RFC PATCH 00/16] 1GB THP support on x86_64 Jason Gunthorpe
2020-09-02 18:45   ` Zi Yan
2020-09-02 18:48     ` Jason Gunthorpe
2020-09-02 19:05       ` Zi Yan
2020-09-02 19:57         ` Jason Gunthorpe [this message]
2020-09-02 20:29           ` Zi Yan
2020-09-03 16:40             ` Jason Gunthorpe
2020-09-03 16:55               ` Matthew Wilcox
2020-09-03 17:08                 ` Jason Gunthorpe
2020-09-03  7:32 ` Michal Hocko
2020-09-03 16:25   ` Roman Gushchin
2020-09-03 16:50     ` Jason Gunthorpe
2020-09-03 17:01       ` Matthew Wilcox
2020-09-03 17:18         ` Jason Gunthorpe
2020-09-03 20:57     ` Mike Kravetz
2020-09-03 21:06       ` Roman Gushchin
2020-09-04  7:42     ` Michal Hocko
2020-09-04 21:10       ` Roman Gushchin
2020-09-07  7:20         ` Michal Hocko
2020-09-08 15:09           ` Zi Yan
2020-09-08 19:58             ` Roman Gushchin
2020-09-09  4:01               ` John Hubbard
2020-09-09  7:15               ` Michal Hocko
2020-09-03 14:23 ` Kirill A. Shutemov
2020-09-03 16:30   ` Roman Gushchin
2020-09-08 11:57     ` David Hildenbrand
2020-09-08 14:05       ` Zi Yan
2020-09-08 14:22         ` David Hildenbrand
2020-09-08 15:36           ` Zi Yan
2020-09-08 14:27         ` Matthew Wilcox
2020-09-08 15:50           ` Zi Yan
2020-09-09 12:11           ` Jason Gunthorpe
2020-09-09 12:32             ` Matthew Wilcox
2020-09-09 13:14               ` Jason Gunthorpe
2020-09-09 13:27                 ` David Hildenbrand
2020-09-10 10:02                   ` William Kucharski
2020-09-08 14:35         ` Michal Hocko
2020-09-08 14:41           ` Rik van Riel
2020-09-08 15:02             ` David Hildenbrand
2020-09-09  7:04             ` Michal Hocko
2020-09-09 13:19               ` Rik van Riel
2020-09-09 13:43                 ` David Hildenbrand
2020-09-09 13:49                   ` Rik van Riel
2020-09-09 13:54                     ` David Hildenbrand
2020-09-10  7:32                   ` Michal Hocko
2020-09-10  8:27                     ` David Hildenbrand
2020-09-10 14:21                       ` Zi Yan
2020-09-10 14:34                         ` David Hildenbrand
2020-09-10 14:41                           ` Zi Yan
2020-09-10 15:15                             ` David Hildenbrand
2020-09-10 13:32                     ` Rik van Riel
2020-09-10 14:30                       ` Zi Yan
2020-09-09 13:59                 ` Michal Hocko

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