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From: Dan Williams <dan.j.williams@intel.com>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: Linux MM <linux-mm@kvack.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	Matthew Wilcox <willy@infradead.org>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Muchun Song <songmuchun@bytedance.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH RFC 0/9] mm, sparse-vmemmap: Introduce compound pagemaps
Date: Tue, 23 Feb 2021 10:15:12 -0800	[thread overview]
Message-ID: <CAPcyv4gdL3p-RVKSVGPfSdBWW+eakTHqCYZp2hqV4QiXCv6KTw@mail.gmail.com> (raw)
In-Reply-To: <1cf0adb0-9692-bcb2-4d3d-374ba3164994@oracle.com>

On Tue, Feb 23, 2021 at 9:16 AM Joao Martins <joao.m.martins@oracle.com> wrote:
>
> On 2/23/21 4:44 PM, Dan Williams wrote:
> > On Tue, Feb 23, 2021 at 8:30 AM Joao Martins <joao.m.martins@oracle.com> wrote:
> >>
> >> On 2/20/21 1:18 AM, Dan Williams wrote:
> >>> On Tue, Dec 8, 2020 at 9:32 AM Joao Martins <joao.m.martins@oracle.com> wrote:
> >>>> Patch 6 - 8: Optimize grabbing/release a page refcount changes given that we
> >>>> are working with compound pages i.e. we do 1 increment/decrement to the head
> >>>> page for a given set of N subpages compared as opposed to N individual writes.
> >>>> {get,pin}_user_pages_fast() for zone_device with compound pagemap consequently
> >>>> improves considerably, and unpin_user_pages() improves as well when passed a
> >>>> set of consecutive pages:
> >>>>
> >>>>                                            before          after
> >>>>     (get_user_pages_fast 1G;2M page size) ~75k  us -> ~3.2k ; ~5.2k us
> >>>>     (pin_user_pages_fast 1G;2M page size) ~125k us -> ~3.4k ; ~5.5k us
> >>>
> >>> Compelling!
> >>>
> >>
> >> BTW is there any reason why we don't support pin_user_pages_fast() with FOLL_LONGTERM for
> >> device-dax?
> >>
> >
> > Good catch.
> >
> > Must have been an oversight of the conversion. FOLL_LONGTERM collides
> > with filesystem operations, but not device-dax.
>
> hmmmm, fwiw, it was unilaterally disabled for any devmap pmd/pud in commit 7af75561e171
> ("mm/gup: add FOLL_LONGTERM capability to GUP fast") and I must only assume that
> by "DAX pages" the submitter was only referring to fs-dax pages.

Agree, that was an fsdax only assumption. Maybe this went unnoticed
because the primary gup-fast case for direct-I/O was not impacted.
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  reply	other threads:[~2021-02-23 18:15 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-08 17:28 [PATCH RFC 0/9] mm, sparse-vmemmap: Introduce compound pagemaps Joao Martins
2020-12-08 17:28 ` [PATCH RFC 1/9] memremap: add ZONE_DEVICE support for compound pages Joao Martins
2020-12-09  5:59   ` John Hubbard
2020-12-09  6:33     ` Matthew Wilcox
2020-12-09 13:12       ` Joao Martins
2021-02-20  1:43     ` Dan Williams
2021-02-22 11:24       ` Joao Martins
2021-02-22 20:37         ` Dan Williams
2021-02-23 15:46           ` Joao Martins
2021-02-23 16:50             ` Dan Williams
2021-02-23 17:18               ` Joao Martins
2021-02-23 18:18                 ` Dan Williams
2021-03-10 18:12           ` Joao Martins
2021-03-12  5:54             ` Dan Williams
2021-02-20  1:24   ` Dan Williams
2021-02-22 11:09     ` Joao Martins
2020-12-08 17:28 ` [PATCH RFC 2/9] sparse-vmemmap: Consolidate arguments in vmemmap section populate Joao Martins
2020-12-09  6:16   ` John Hubbard
2020-12-09 13:51     ` Joao Martins
2021-02-20  1:49   ` Dan Williams
2021-02-22 11:26     ` Joao Martins
2020-12-08 17:28 ` [PATCH RFC 3/9] sparse-vmemmap: Reuse vmemmap areas for a given mhp_params::align Joao Martins
2020-12-08 17:38   ` Joao Martins
2020-12-08 17:28 ` [PATCH RFC 3/9] sparse-vmemmap: Reuse vmemmap areas for a given page size Joao Martins
2021-02-20  3:34   ` Dan Williams
2021-02-22 11:42     ` Joao Martins
2021-02-22 22:40       ` Dan Williams
2021-02-23 15:46         ` Joao Martins
2020-12-08 17:28 ` [PATCH RFC 4/9] mm/page_alloc: Reuse tail struct pages for compound pagemaps Joao Martins
2021-02-20  6:17   ` Dan Williams
2021-02-22 12:01     ` Joao Martins
2020-12-08 17:28 ` [PATCH RFC 5/9] device-dax: Compound pagemap support Joao Martins
2020-12-08 17:28 ` [PATCH RFC 6/9] mm/gup: Grab head page refcount once for group of subpages Joao Martins
2020-12-09  4:40   ` John Hubbard
2020-12-09 13:44     ` Joao Martins
     [not found]   ` <20201208194905.GQ5487@ziepe.ca>
2020-12-09 11:05     ` Joao Martins
     [not found]       ` <20201209151505.GV5487@ziepe.ca>
2020-12-09 16:02         ` Joao Martins
     [not found]           ` <20201209162438.GW5487@ziepe.ca>
2020-12-09 17:27             ` Joao Martins
2020-12-09 18:14             ` Matthew Wilcox
2020-12-10 15:43               ` Joao Martins
2020-12-08 17:28 ` [PATCH RFC 7/9] mm/gup: Decrement head page " Joao Martins
     [not found]   ` <20201208193446.GP5487@ziepe.ca>
2020-12-09  5:06     ` John Hubbard
2020-12-09 12:17     ` Joao Martins
2020-12-17 19:05     ` Joao Martins
     [not found]       ` <20201217200530.GK5487@ziepe.ca>
2020-12-17 22:34         ` Joao Martins
2020-12-19  2:06         ` John Hubbard
2020-12-19 13:10           ` Joao Martins
2020-12-08 17:29 ` [PATCH RFC 8/9] RDMA/umem: batch page unpin in __ib_mem_release() Joao Martins
2020-12-09  5:18   ` John Hubbard
     [not found]   ` <20201208192935.GA1908088@ziepe.ca>
2020-12-09 10:59     ` Joao Martins
2020-12-19 13:15       ` Joao Martins
2020-12-08 17:29 ` [PATCH RFC 9/9] mm: Add follow_devmap_page() for devdax vmas Joao Martins
2020-12-09  5:23   ` John Hubbard
     [not found]   ` <20201208195754.GR5487@ziepe.ca>
2020-12-09  8:05     ` Christoph Hellwig
2020-12-09 11:19     ` Joao Martins
2020-12-09  9:38 ` [PATCH RFC 0/9] mm, sparse-vmemmap: Introduce compound pagemaps David Hildenbrand
2020-12-09  9:52 ` [External] " Muchun Song
2021-02-20  1:18 ` Dan Williams
2021-02-22 11:06   ` Joao Martins
2021-02-22 14:32     ` Joao Martins
2021-02-23 16:28   ` Joao Martins
2021-02-23 16:44     ` Dan Williams
2021-02-23 17:15       ` Joao Martins
2021-02-23 18:15         ` Dan Williams [this message]
     [not found]       ` <20210223185435.GO2643399@ziepe.ca>
2021-02-23 22:48         ` Dan Williams
     [not found]           ` <20210223230723.GP2643399@ziepe.ca>
2021-02-24  0:14             ` Dan Williams
     [not found]               ` <20210224010017.GQ2643399@ziepe.ca>
2021-02-24  1:32                 ` Dan Williams

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