From: John Hubbard <jhubbard@nvidia.com>
To: Joao Martins <joao.m.martins@oracle.com>, <linux-mm@kvack.org>
Cc: 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@ml01.01.org
Subject: Re: [PATCH RFC 1/9] memremap: add ZONE_DEVICE support for compound pages
Date: Tue, 8 Dec 2020 21:59:19 -0800 [thread overview]
Message-ID: <7249cfd2-c178-2e6a-6b03-307a05f11785@nvidia.com> (raw)
In-Reply-To: <20201208172901.17384-2-joao.m.martins@oracle.com>
On 12/8/20 9:28 AM, Joao Martins wrote:
> Add a new flag for struct dev_pagemap which designates that a a pagemap
a a
> is described as a set of compound pages or in other words, that how
> pages are grouped together in the page tables are reflected in how we
> describe struct pages. This means that rather than initializing
> individual struct pages, we also initialize these struct pages, as
Let's not say "rather than x, we also do y", because it's self-contradictory.
I think you want to just leave out the "also", like this:
"This means that rather than initializing> individual struct pages, we
initialize these struct pages ..."
Is that right?
> compound pages (on x86: 2M or 1G compound pages)
>
> For certain ZONE_DEVICE users, like device-dax, which have a fixed page
> size, this creates an opportunity to optimize GUP and GUP-fast walkers,
> thus playing the same tricks as hugetlb pages.
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
> include/linux/memremap.h | 2 ++
> mm/memremap.c | 8 ++++++--
> mm/page_alloc.c | 7 +++++++
> 3 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index 79c49e7f5c30..f8f26b2cc3da 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -90,6 +90,7 @@ struct dev_pagemap_ops {
> };
>
> #define PGMAP_ALTMAP_VALID (1 << 0)
> +#define PGMAP_COMPOUND (1 << 1)
>
> /**
> * struct dev_pagemap - metadata for ZONE_DEVICE mappings
> @@ -114,6 +115,7 @@ struct dev_pagemap {
> struct completion done;
> enum memory_type type;
> unsigned int flags;
> + unsigned int align;
This also needs an "@aline" entry in the comment block above.
> const struct dev_pagemap_ops *ops;
> void *owner;
> int nr_range;
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 16b2fb482da1..287a24b7a65a 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -277,8 +277,12 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
> memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
> PHYS_PFN(range->start),
> PHYS_PFN(range_len(range)), pgmap);
> - percpu_ref_get_many(pgmap->ref, pfn_end(pgmap, range_id)
> - - pfn_first(pgmap, range_id));
> + if (pgmap->flags & PGMAP_COMPOUND)
> + percpu_ref_get_many(pgmap->ref, (pfn_end(pgmap, range_id)
> + - pfn_first(pgmap, range_id)) / PHYS_PFN(pgmap->align));
Is there some reason that we cannot use range_len(), instead of pfn_end() minus
pfn_first()? (Yes, this more about the pre-existing code than about your change.)
And if not, then why are the nearby range_len() uses OK? I realize that range_len()
is simpler and skips a case, but it's not clear that it's required here. But I'm
new to this area so be warned. :)
Also, dividing by PHYS_PFN() feels quite misleading: that function does what you
happen to want, but is not named accordingly. Can you use or create something
more accurately named? Like "number of pages in this large page"?
> + else
> + percpu_ref_get_many(pgmap->ref, pfn_end(pgmap, range_id)
> + - pfn_first(pgmap, range_id));
> return 0;
>
> err_add_memory:
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index eaa227a479e4..9716ecd58e29 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6116,6 +6116,8 @@ void __ref memmap_init_zone_device(struct zone *zone,
> unsigned long pfn, end_pfn = start_pfn + nr_pages;
> struct pglist_data *pgdat = zone->zone_pgdat;
> struct vmem_altmap *altmap = pgmap_altmap(pgmap);
> + bool compound = pgmap->flags & PGMAP_COMPOUND;
> + unsigned int align = PHYS_PFN(pgmap->align);
Maybe align_pfn or pfn_align? Don't want the same name for things that are actually
different types, in meaning anyway.
> unsigned long zone_idx = zone_idx(zone);
> unsigned long start = jiffies;
> int nid = pgdat->node_id;
> @@ -6171,6 +6173,11 @@ void __ref memmap_init_zone_device(struct zone *zone,
> }
> }
>
> + if (compound) {
> + for (pfn = start_pfn; pfn < end_pfn; pfn += align)
> + prep_compound_page(pfn_to_page(pfn), order_base_2(align));
> + }
> +
> pr_info("%s initialised %lu pages in %ums\n", __func__,
> nr_pages, jiffies_to_msecs(jiffies - start));
> }
>
thanks,
--
John Hubbard
NVIDIA
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next prev parent reply other threads:[~2020-12-09 5:59 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 [this message]
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
[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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