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From: Muchun Song <songmuchun@bytedance.com>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: Linux Memory Management List <linux-mm@kvack.org>,
	linux-nvdimm@lists.01.org, Matthew Wilcox <willy@infradead.org>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [External] [PATCH RFC 0/9] mm, sparse-vmemmap: Introduce compound pagemaps
Date: Wed, 9 Dec 2020 17:52:10 +0800	[thread overview]
Message-ID: <CAMZfGtXLcOPZ6Frwj574ZzcZ3Qr5Kzv2t-FCDDDONUvPymYQLA@mail.gmail.com> (raw)
In-Reply-To: <20201208172901.17384-1-joao.m.martins@oracle.com>

On Wed, Dec 9, 2020 at 1:32 AM Joao Martins <joao.m.martins@oracle.com> wrote:
>
> Hey,
>
> This small series, attempts at minimizing 'struct page' overhead by
> pursuing a similar approach as Muchun Song series "Free some vmemmap
> pages of hugetlb page"[0] but applied to devmap/ZONE_DEVICE.
>
> [0] https://lore.kernel.org/linux-mm/20201130151838.11208-1-songmuchun@bytedance.com/
>

Oh, well. It looks like you agree with my optimization approach
and have fully understood. Also, welcome help me review that
series if you have time. :)

> The link above describes it quite nicely, but the idea is to reuse tail
> page vmemmap areas, particular the area which only describes tail pages.
> So a vmemmap page describes 64 struct pages, and the first page for a given
> ZONE_DEVICE vmemmap would contain the head page and 63 tail pages. The second
> vmemmap page would contain only tail pages, and that's what gets reused across
> the rest of the subsection/section. The bigger the page size, the bigger the
> savings (2M hpage -> save 6 vmemmap pages; 1G hpage -> save 4094 vmemmap pages).
>
> In terms of savings, per 1Tb of memory, the struct page cost would go down
> with compound pagemap:
>
> * with 2M pages we lose 4G instead of 16G (0.39% instead of 1.5% of total memory)
> * with 1G pages we lose 8MB instead of 16G (0.0007% instead of 1.5% of total memory)
>
> Along the way I've extended it past 'struct page' overhead *trying* to address a
> few performance issues we knew about for pmem, specifically on the
> {pin,get}_user_pages* function family with device-dax vmas which are really
> slow even of the fast variants. THP is great on -fast variants but all except
> hugetlbfs perform rather poorly on non-fast gup.
>
> So to summarize what the series does:
>
> Patches 1-5: Much like Muchun series, we reuse tail page areas across a given
> page size (namely @align was referred by remaining memremap/dax code) and
> enabling of memremap to initialize the ZONE_DEVICE pages as compound pages or a
> given @align order. The main difference though, is that contrary to the hugetlbfs
> series, there's no vmemmap for the area, because we are onlining it. IOW no
> freeing of pages of already initialized vmemmap like the case for hugetlbfs,
> which simplifies the logic (besides not being arch-specific). After these,
> there's quite visible region bootstrap of pmem memmap given that we would
> initialize fewer struct pages depending on the page size.
>
>     NVDIMM namespace bootstrap improves from ~750ms to ~190ms/<=1ms on emulated NVDIMMs
>     with 2M and 1G respectivally. The net gain in improvement is similarly observed
>     in proportion when running on actual NVDIMMs.
>
> 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
>
> The RDMA patch (patch 8/9) is to demonstrate the improvement for an existing
> user. For unpin_user_pages() we have an additional test to demonstrate the
> improvement.  The test performs MR reg/unreg continuously and measuring its
> rate for a given period. So essentially ib_mem_get and ib_mem_release being
> stress tested which at the end of day means: pin_user_pages_longterm() and
> unpin_user_pages() for a scatterlist:
>
>     Before:
>     159 rounds in 5.027 sec: 31617.923 usec / round (device-dax)
>     466 rounds in 5.009 sec: 10748.456 usec / round (hugetlbfs)
>
>     After:
>     305 rounds in 5.010 sec: 16426.047 usec / round (device-dax)
>     1073 rounds in 5.004 sec: 4663.622 usec / round (hugetlbfs)
>
> Patch 9: Improves {pin,get}_user_pages() and its longterm counterpart. It
> is very experimental, and I imported most of follow_hugetlb_page(), except
> that we do the same trick as gup-fast. In doing the patch I feel this batching
> should live in follow_page_mask() and having that being changed to return a set
> of pages/something-else when walking over PMD/PUDs for THP / devmap pages. This
> patch then brings the previous test of mr reg/unreg (above) on parity
> between device-dax and hugetlbfs.
>
> Some of the patches are a little fresh/WIP (specially patch 3 and 9) and we are
> still running tests. Hence the RFC, asking for comments and general direction
> of the work before continuing.
>
> Patches apply on top of linux-next tag next-20201208 (commit a9e26cb5f261).
>
> Comments and suggestions very much appreciated!
>
> Thanks,
>         Joao
>
> Joao Martins (9):
>   memremap: add ZONE_DEVICE support for compound pages
>   sparse-vmemmap: Consolidate arguments in vmemmap section populate
>   sparse-vmemmap: Reuse vmemmap areas for a given page size
>   mm/page_alloc: Reuse tail struct pages for compound pagemaps
>   device-dax: Compound pagemap support
>   mm/gup: Grab head page refcount once for group of subpages
>   mm/gup: Decrement head page once for group of subpages
>   RDMA/umem: batch page unpin in __ib_mem_release()
>   mm: Add follow_devmap_page() for devdax vmas
>
>  drivers/dax/device.c           |  54 ++++++---
>  drivers/infiniband/core/umem.c |  25 +++-
>  include/linux/huge_mm.h        |   4 +
>  include/linux/memory_hotplug.h |  16 ++-
>  include/linux/memremap.h       |   2 +
>  include/linux/mm.h             |   6 +-
>  mm/gup.c                       | 130 ++++++++++++++++-----
>  mm/huge_memory.c               | 202 +++++++++++++++++++++++++++++++++
>  mm/memory_hotplug.c            |  13 ++-
>  mm/memremap.c                  |  13 ++-
>  mm/page_alloc.c                |  28 ++++-
>  mm/sparse-vmemmap.c            |  97 +++++++++++++---
>  mm/sparse.c                    |  16 +--
>  13 files changed, 531 insertions(+), 75 deletions(-)
>
> --
> 2.17.1
>


-- 
Yours,
Muchun
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WARNING: multiple messages have this Message-ID
From: Muchun Song <songmuchun@bytedance.com>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: Linux Memory Management List <linux-mm@kvack.org>,
	Dan Williams <dan.j.williams@intel.com>,
	 Ira Weiny <ira.weiny@intel.com>,
	linux-nvdimm@lists.01.org,  Matthew Wilcox <willy@infradead.org>,
	Jason Gunthorpe <jgg@ziepe.ca>, Jane Chu <jane.chu@oracle.com>,
	 Mike Kravetz <mike.kravetz@oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [External] [PATCH RFC 0/9] mm, sparse-vmemmap: Introduce compound pagemaps
Date: Wed, 9 Dec 2020 17:52:10 +0800	[thread overview]
Message-ID: <CAMZfGtXLcOPZ6Frwj574ZzcZ3Qr5Kzv2t-FCDDDONUvPymYQLA@mail.gmail.com> (raw)
In-Reply-To: <20201208172901.17384-1-joao.m.martins@oracle.com>

On Wed, Dec 9, 2020 at 1:32 AM Joao Martins <joao.m.martins@oracle.com> wrote:
>
> Hey,
>
> This small series, attempts at minimizing 'struct page' overhead by
> pursuing a similar approach as Muchun Song series "Free some vmemmap
> pages of hugetlb page"[0] but applied to devmap/ZONE_DEVICE.
>
> [0] https://lore.kernel.org/linux-mm/20201130151838.11208-1-songmuchun@bytedance.com/
>

Oh, well. It looks like you agree with my optimization approach
and have fully understood. Also, welcome help me review that
series if you have time. :)

> The link above describes it quite nicely, but the idea is to reuse tail
> page vmemmap areas, particular the area which only describes tail pages.
> So a vmemmap page describes 64 struct pages, and the first page for a given
> ZONE_DEVICE vmemmap would contain the head page and 63 tail pages. The second
> vmemmap page would contain only tail pages, and that's what gets reused across
> the rest of the subsection/section. The bigger the page size, the bigger the
> savings (2M hpage -> save 6 vmemmap pages; 1G hpage -> save 4094 vmemmap pages).
>
> In terms of savings, per 1Tb of memory, the struct page cost would go down
> with compound pagemap:
>
> * with 2M pages we lose 4G instead of 16G (0.39% instead of 1.5% of total memory)
> * with 1G pages we lose 8MB instead of 16G (0.0007% instead of 1.5% of total memory)
>
> Along the way I've extended it past 'struct page' overhead *trying* to address a
> few performance issues we knew about for pmem, specifically on the
> {pin,get}_user_pages* function family with device-dax vmas which are really
> slow even of the fast variants. THP is great on -fast variants but all except
> hugetlbfs perform rather poorly on non-fast gup.
>
> So to summarize what the series does:
>
> Patches 1-5: Much like Muchun series, we reuse tail page areas across a given
> page size (namely @align was referred by remaining memremap/dax code) and
> enabling of memremap to initialize the ZONE_DEVICE pages as compound pages or a
> given @align order. The main difference though, is that contrary to the hugetlbfs
> series, there's no vmemmap for the area, because we are onlining it. IOW no
> freeing of pages of already initialized vmemmap like the case for hugetlbfs,
> which simplifies the logic (besides not being arch-specific). After these,
> there's quite visible region bootstrap of pmem memmap given that we would
> initialize fewer struct pages depending on the page size.
>
>     NVDIMM namespace bootstrap improves from ~750ms to ~190ms/<=1ms on emulated NVDIMMs
>     with 2M and 1G respectivally. The net gain in improvement is similarly observed
>     in proportion when running on actual NVDIMMs.
>
> 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
>
> The RDMA patch (patch 8/9) is to demonstrate the improvement for an existing
> user. For unpin_user_pages() we have an additional test to demonstrate the
> improvement.  The test performs MR reg/unreg continuously and measuring its
> rate for a given period. So essentially ib_mem_get and ib_mem_release being
> stress tested which at the end of day means: pin_user_pages_longterm() and
> unpin_user_pages() for a scatterlist:
>
>     Before:
>     159 rounds in 5.027 sec: 31617.923 usec / round (device-dax)
>     466 rounds in 5.009 sec: 10748.456 usec / round (hugetlbfs)
>
>     After:
>     305 rounds in 5.010 sec: 16426.047 usec / round (device-dax)
>     1073 rounds in 5.004 sec: 4663.622 usec / round (hugetlbfs)
>
> Patch 9: Improves {pin,get}_user_pages() and its longterm counterpart. It
> is very experimental, and I imported most of follow_hugetlb_page(), except
> that we do the same trick as gup-fast. In doing the patch I feel this batching
> should live in follow_page_mask() and having that being changed to return a set
> of pages/something-else when walking over PMD/PUDs for THP / devmap pages. This
> patch then brings the previous test of mr reg/unreg (above) on parity
> between device-dax and hugetlbfs.
>
> Some of the patches are a little fresh/WIP (specially patch 3 and 9) and we are
> still running tests. Hence the RFC, asking for comments and general direction
> of the work before continuing.
>
> Patches apply on top of linux-next tag next-20201208 (commit a9e26cb5f261).
>
> Comments and suggestions very much appreciated!
>
> Thanks,
>         Joao
>
> Joao Martins (9):
>   memremap: add ZONE_DEVICE support for compound pages
>   sparse-vmemmap: Consolidate arguments in vmemmap section populate
>   sparse-vmemmap: Reuse vmemmap areas for a given page size
>   mm/page_alloc: Reuse tail struct pages for compound pagemaps
>   device-dax: Compound pagemap support
>   mm/gup: Grab head page refcount once for group of subpages
>   mm/gup: Decrement head page once for group of subpages
>   RDMA/umem: batch page unpin in __ib_mem_release()
>   mm: Add follow_devmap_page() for devdax vmas
>
>  drivers/dax/device.c           |  54 ++++++---
>  drivers/infiniband/core/umem.c |  25 +++-
>  include/linux/huge_mm.h        |   4 +
>  include/linux/memory_hotplug.h |  16 ++-
>  include/linux/memremap.h       |   2 +
>  include/linux/mm.h             |   6 +-
>  mm/gup.c                       | 130 ++++++++++++++++-----
>  mm/huge_memory.c               | 202 +++++++++++++++++++++++++++++++++
>  mm/memory_hotplug.c            |  13 ++-
>  mm/memremap.c                  |  13 ++-
>  mm/page_alloc.c                |  28 ++++-
>  mm/sparse-vmemmap.c            |  97 +++++++++++++---
>  mm/sparse.c                    |  16 +--
>  13 files changed, 531 insertions(+), 75 deletions(-)
>
> --
> 2.17.1
>


-- 
Yours,
Muchun


  parent reply	other threads:[~2020-12-09  9:52 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 ` Muchun Song [this message]
2020-12-09  9:52   ` [External] " 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
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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