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From: Joao Martins <joao.m.martins@oracle.com>
To: Dan Williams <dan.j.williams@intel.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 17:15:04 +0000	[thread overview]
Message-ID: <1cf0adb0-9692-bcb2-4d3d-374ba3164994@oracle.com> (raw)
In-Reply-To: <CAPcyv4joomjhZYaCBNrYjvATSYgECfHYOZy=n_QVKqX7D_ReZQ@mail.gmail.com>

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.

> In fact that's the
> motivation for device-dax in the first instance, no need to coordinate
> runtime physical address layout changes because the device is
> statically allocated.
> 
/me nods

>> Looking at the history, I understand that fsdax can't support it atm, but I am not sure
>> that the same holds for device-dax. I have this small chunk (see below the scissors mark)
>> which relaxes this for a pgmap of type MEMORY_DEVICE_GENERIC, albeit not sure if there is
>> a fundamental issue for the other types that makes this an unwelcoming change.
>>
>>         Joao
>>
>> --------------------->8---------------------
>>
>> Subject: [PATCH] mm/gup: allow FOLL_LONGTERM pin-fast for
>>  MEMORY_DEVICE_GENERIC
>>
>> The downside would be one extra lookup in dev_pagemap tree
>> for other pgmap->types (P2P, FSDAX, PRIVATE). But just one
>> per gup-fast() call.
> 
> I'd guess a dev_pagemap lookup is faster than a get_user_pages slow
> path. It should be measurable that this change is at least as fast or
> faster than falling back to the slow path, but it would be good to
> measure.
> 
But with the changes I am/will-be making I hope gup-fast and gup-slow
will be as fast (for present pmd/puds ofc, as the fault makes it slower).

I'll formally submit below patch, once I ran over the numbers.

> Code changes look good to me.
> 
Cool! Will add in the suggested change below.

>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>>  include/linux/mm.h |  5 +++++
>>  mm/gup.c           | 24 +++++++++++++-----------
>>  2 files changed, 18 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 32f0c3986d4f..c89a049bbd7a 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1171,6 +1171,11 @@ static inline bool is_pci_p2pdma_page(const struct page *page)
>>                 page->pgmap->type == MEMORY_DEVICE_PCI_P2PDMA;
>>  }
>>
>> +static inline bool devmap_longterm_available(const struct dev_pagemap *pgmap)
>> +{
> 
> I'd call this devmap_can_longterm().
> 
Ack.
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WARNING: multiple messages have this Message-ID
From: Joao Martins <joao.m.martins@oracle.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Linux MM <linux-mm@kvack.org>, Ira Weiny <ira.weiny@intel.com>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	Matthew Wilcox <willy@infradead.org>,
	Jason Gunthorpe <jgg@ziepe.ca>, Jane Chu <jane.chu@oracle.com>,
	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 17:15:04 +0000	[thread overview]
Message-ID: <1cf0adb0-9692-bcb2-4d3d-374ba3164994@oracle.com> (raw)
In-Reply-To: <CAPcyv4joomjhZYaCBNrYjvATSYgECfHYOZy=n_QVKqX7D_ReZQ@mail.gmail.com>

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.

> In fact that's the
> motivation for device-dax in the first instance, no need to coordinate
> runtime physical address layout changes because the device is
> statically allocated.
> 
/me nods

>> Looking at the history, I understand that fsdax can't support it atm, but I am not sure
>> that the same holds for device-dax. I have this small chunk (see below the scissors mark)
>> which relaxes this for a pgmap of type MEMORY_DEVICE_GENERIC, albeit not sure if there is
>> a fundamental issue for the other types that makes this an unwelcoming change.
>>
>>         Joao
>>
>> --------------------->8---------------------
>>
>> Subject: [PATCH] mm/gup: allow FOLL_LONGTERM pin-fast for
>>  MEMORY_DEVICE_GENERIC
>>
>> The downside would be one extra lookup in dev_pagemap tree
>> for other pgmap->types (P2P, FSDAX, PRIVATE). But just one
>> per gup-fast() call.
> 
> I'd guess a dev_pagemap lookup is faster than a get_user_pages slow
> path. It should be measurable that this change is at least as fast or
> faster than falling back to the slow path, but it would be good to
> measure.
> 
But with the changes I am/will-be making I hope gup-fast and gup-slow
will be as fast (for present pmd/puds ofc, as the fault makes it slower).

I'll formally submit below patch, once I ran over the numbers.

> Code changes look good to me.
> 
Cool! Will add in the suggested change below.

>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>>  include/linux/mm.h |  5 +++++
>>  mm/gup.c           | 24 +++++++++++++-----------
>>  2 files changed, 18 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 32f0c3986d4f..c89a049bbd7a 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1171,6 +1171,11 @@ static inline bool is_pci_p2pdma_page(const struct page *page)
>>                 page->pgmap->type == MEMORY_DEVICE_PCI_P2PDMA;
>>  }
>>
>> +static inline bool devmap_longterm_available(const struct dev_pagemap *pgmap)
>> +{
> 
> I'd call this devmap_can_longterm().
> 
Ack.


  reply	other threads:[~2021-02-23 17:15 UTC|newest]

Thread overview: 147+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-08 17:28 Joao Martins
2020-12-08 17:28 ` Joao Martins
2020-12-08 17:28 ` [PATCH RFC 1/9] memremap: add ZONE_DEVICE support for compound pages Joao Martins
2020-12-08 17:28   ` Joao Martins
2020-12-09  5:59   ` John Hubbard
2020-12-09  5:59     ` John Hubbard
2020-12-09  6:33     ` Matthew Wilcox
2020-12-09  6:33       ` Matthew Wilcox
2020-12-09 13:12       ` Joao Martins
2020-12-09 13:12         ` Joao Martins
2021-02-20  1:43     ` Dan Williams
2021-02-20  1:43       ` Dan Williams
2021-02-22 11:24       ` Joao Martins
2021-02-22 11:24         ` Joao Martins
2021-02-22 20:37         ` Dan Williams
2021-02-22 20:37           ` Dan Williams
2021-02-23 15:46           ` Joao Martins
2021-02-23 15:46             ` Joao Martins
2021-02-23 16:50             ` Dan Williams
2021-02-23 16:50               ` Dan Williams
2021-02-23 17:18               ` Joao Martins
2021-02-23 17:18                 ` Joao Martins
2021-02-23 18:18                 ` Dan Williams
2021-02-23 18:18                   ` Dan Williams
2021-03-10 18:12           ` Joao Martins
2021-03-10 18:12             ` Joao Martins
2021-03-12  5:54             ` Dan Williams
2021-03-12  5:54               ` Dan Williams
2021-02-20  1:24   ` Dan Williams
2021-02-20  1:24     ` Dan Williams
2021-02-22 11:09     ` Joao Martins
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
2020-12-08 17:28   ` Joao Martins
2020-12-09  6:16   ` John Hubbard
2020-12-09  6:16     ` John Hubbard
2020-12-09 13:51     ` Joao Martins
2020-12-09 13:51       ` Joao Martins
2021-02-20  1:49   ` Dan Williams
2021-02-20  1:49     ` Dan Williams
2021-02-22 11:26     ` Joao Martins
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 17:28   ` Joao Martins
2020-12-08 17:38   ` 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
2020-12-08 17:28   ` Joao Martins
2021-02-20  3:34   ` Dan Williams
2021-02-20  3:34     ` Dan Williams
2021-02-22 11:42     ` Joao Martins
2021-02-22 11:42       ` Joao Martins
2021-02-22 22:40       ` Dan Williams
2021-02-22 22:40         ` Dan Williams
2021-02-23 15:46         ` Joao Martins
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
2020-12-08 17:28   ` Joao Martins
2021-02-20  6:17   ` Dan Williams
2021-02-20  6:17     ` Dan Williams
2021-02-22 12:01     ` Joao Martins
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   ` Joao Martins
2020-12-08 17:28 ` [PATCH RFC 6/9] mm/gup: Grab head page refcount once for group of subpages Joao Martins
2020-12-08 17:28   ` Joao Martins
2020-12-08 19:49   ` Jason Gunthorpe
2020-12-09 11:05     ` Joao Martins
2020-12-09 11:05       ` Joao Martins
2020-12-09 15:15       ` Jason Gunthorpe
2020-12-09 16:02         ` Joao Martins
2020-12-09 16:02           ` Joao Martins
2020-12-09 16:24           ` Jason Gunthorpe
2020-12-09 17:27             ` Joao Martins
2020-12-09 17:27               ` Joao Martins
2020-12-09 18:14             ` Matthew Wilcox
2020-12-09 18:14               ` Matthew Wilcox
2020-12-09 19:08               ` Jason Gunthorpe
2020-12-10 15:43               ` Joao Martins
2020-12-10 15:43                 ` Joao Martins
2020-12-09  4:40   ` John Hubbard
2020-12-09  4:40     ` John Hubbard
2020-12-09 13:44     ` Joao Martins
2020-12-09 13:44       ` Joao Martins
2020-12-08 17:28 ` [PATCH RFC 7/9] mm/gup: Decrement head page " Joao Martins
2020-12-08 17:28   ` Joao Martins
2020-12-08 19:34   ` Jason Gunthorpe
2020-12-09  5:06     ` John Hubbard
2020-12-09  5:06       ` John Hubbard
2020-12-09 13:43       ` Jason Gunthorpe
2020-12-09 12:17     ` Joao Martins
2020-12-09 12:17       ` Joao Martins
2020-12-17 19:05     ` Joao Martins
2020-12-17 19:05       ` Joao Martins
2020-12-17 20:05       ` Jason Gunthorpe
2020-12-17 22:34         ` Joao Martins
2020-12-17 22:34           ` Joao Martins
2020-12-18 14:25           ` Jason Gunthorpe
2020-12-19  2:06         ` John Hubbard
2020-12-19  2:06           ` John Hubbard
2020-12-19 13:10           ` Joao Martins
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
2020-12-08 17:29   ` Joao Martins
2020-12-08 19:29   ` Jason Gunthorpe
2020-12-09 10:59     ` Joao Martins
2020-12-09 10:59       ` Joao Martins
2020-12-19 13:15       ` Joao Martins
2020-12-19 13:15         ` Joao Martins
2020-12-09  5:18   ` John Hubbard
2020-12-09  5:18     ` John Hubbard
2020-12-08 17:29 ` [PATCH RFC 9/9] mm: Add follow_devmap_page() for devdax vmas Joao Martins
2020-12-08 17:29   ` Joao Martins
2020-12-08 19:57   ` Jason Gunthorpe
2020-12-09  8:05     ` Christoph Hellwig
2020-12-09  8:05       ` Christoph Hellwig
2020-12-09 11:19     ` Joao Martins
2020-12-09 11:19       ` Joao Martins
2020-12-09  5:23   ` John Hubbard
2020-12-09  5:23     ` John Hubbard
2020-12-09  9:38 ` [PATCH RFC 0/9] mm, sparse-vmemmap: Introduce compound pagemaps David Hildenbrand
2020-12-09  9:38   ` David Hildenbrand
2020-12-09  9:52 ` [External] " Muchun Song
2020-12-09  9:52   ` Muchun Song
2021-02-20  1:18 ` Dan Williams
2021-02-20  1:18   ` Dan Williams
2021-02-22 11:06   ` Joao Martins
2021-02-22 11:06     ` Joao Martins
2021-02-22 14:32     ` Joao Martins
2021-02-22 14:32       ` Joao Martins
2021-02-23 16:28   ` Joao Martins
2021-02-23 16:28     ` Joao Martins
2021-02-23 16:44     ` Dan Williams
2021-02-23 16:44       ` Dan Williams
2021-02-23 17:15       ` Joao Martins [this message]
2021-02-23 17:15         ` Joao Martins
2021-02-23 18:15         ` Dan Williams
2021-02-23 18:15           ` Dan Williams
2021-02-23 18:54       ` Jason Gunthorpe
2021-02-23 22:48         ` Dan Williams
2021-02-23 22:48           ` Dan Williams
2021-02-23 23:07           ` Jason Gunthorpe
2021-02-24  0:14             ` Dan Williams
2021-02-24  0:14               ` Dan Williams
2021-02-24  1:00               ` Jason Gunthorpe
2021-02-24  1:32                 ` Dan Williams
2021-02-24  1:32                   ` Dan Williams

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