From: Matthew Wilcox <willy@infradead.org>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Dan Williams <dan.j.williams@intel.com>,
Linux MM <linux-mm@kvack.org>, Ira Weiny <ira.weiny@intel.com>,
linux-nvdimm <linux-nvdimm@lists.01.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 v1 04/11] mm/memremap: add ZONE_DEVICE support for compound pages
Date: Thu, 6 May 2021 12:43:57 +0100 [thread overview]
Message-ID: <20210506114357.GA388843@casper.infradead.org> (raw)
In-Reply-To: <31563092-a7b8-e6e1-f5ad-a66c02243a9d@oracle.com>
On Thu, May 06, 2021 at 11:23:25AM +0100, Joao Martins wrote:
> >> I think it is ok for dax/nvdimm to continue to maintain their align
> >> value because it should be ok to have 4MB align if the device really
> >> wanted. However, when it goes to map that alignment with
> >> memremap_pages() it can pick a mode. For example, it's already the
> >> case that dax->align == 1GB is mapped with DEVMAP_PTE today, so
> >> they're already separate concepts that can stay separate.
> >
> > devdax namespace with align of 1G implies we expect to map them with 1G
> > pte entries? I didn't follow when you say we map them today with
> > DEVMAP_PTE entries.
>
> This sort of confusion is largelly why Dan is suggesting a @geometry for naming rather
> than @align (which traditionally refers to page tables entry sizes in pagemap-related stuff).
>
> DEVMAP_{PTE,PMD,PUD} refers to the representation of metadata in base pages (DEVMAP_PTE),
> compound pages of PMD order (DEVMAP_PMD) or compound pages of PUD order (DEVMAP_PUD).
>
> So, today:
>
> * namespaces with align of 1G would use *struct pages of order-0* (DEVMAP_PTE) backed with
> PMD entries in the direct map.
> * namespaces with align of 2M would use *struct pages of order-0* (DEVMAP_PTE) backed with
> PMD entries in the direct map.
>
> After this series:
>
> * namespaces with align of 1G would use *compound struct pages of order-30* (DEVMAP_PUD)
> backed with PMD entries in the direct map.
order-18
> * namespaces with align of 1G would use *compound struct pages of order-21* (DEVMAP_PMD)
> backed with PTE entries in the direct map.
i think you mean "align of 2M", and order-9.
(note that these numbers are/can be different for powerpc since it
supports different TLB page sizes. please don't get locked into x86
sizes, and don't ignore the benefits *to software* of managing memory
in sizes other than just those supported by the hardware).
next prev parent reply other threads:[~2021-05-06 11:45 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-25 23:09 [PATCH v1 00/11] mm, sparse-vmemmap: Introduce compound pagemaps Joao Martins
2021-03-25 23:09 ` [PATCH v1 01/11] memory-failure: fetch compound_head after pgmap_pfn_valid() Joao Martins
2021-04-24 0:12 ` Dan Williams
2021-04-24 19:00 ` Joao Martins
2021-03-25 23:09 ` [PATCH v1 02/11] mm/page_alloc: split prep_compound_page into head and tail subparts Joao Martins
2021-04-24 0:16 ` Dan Williams
2021-04-24 19:05 ` Joao Martins
2021-03-25 23:09 ` [PATCH v1 03/11] mm/page_alloc: refactor memmap_init_zone_device() page init Joao Martins
2021-04-24 0:18 ` Dan Williams
2021-04-24 19:05 ` Joao Martins
2021-03-25 23:09 ` [PATCH v1 04/11] mm/memremap: add ZONE_DEVICE support for compound pages Joao Martins
2021-05-05 18:44 ` Dan Williams
2021-05-05 18:58 ` Matthew Wilcox
2021-05-05 19:49 ` Joao Martins
2021-05-05 22:20 ` Dan Williams
2021-05-05 22:36 ` Joao Martins
2021-05-05 23:03 ` Dan Williams
2021-05-06 10:12 ` Joao Martins
2021-05-18 17:27 ` Joao Martins
2021-05-18 19:56 ` Jane Chu
2021-05-19 11:29 ` Joao Martins
2021-05-19 18:36 ` Jane Chu
2021-06-07 20:17 ` Dan Williams
2021-06-07 20:47 ` Joao Martins
2021-06-07 21:00 ` Joao Martins
2021-06-07 21:57 ` Dan Williams
2021-05-06 8:05 ` Aneesh Kumar K.V
2021-05-06 10:23 ` Joao Martins
2021-05-06 11:43 ` Matthew Wilcox [this message]
2021-05-06 12:15 ` Joao Martins
2021-03-25 23:09 ` [PATCH v1 05/11] mm/sparse-vmemmap: add a pgmap argument to section activation Joao Martins
2021-05-05 22:34 ` Dan Williams
2021-05-05 22:37 ` Joao Martins
2021-05-05 23:14 ` Dan Williams
2021-05-06 10:24 ` Joao Martins
2021-03-25 23:09 ` [PATCH v1 06/11] mm/sparse-vmemmap: refactor vmemmap_populate_basepages() Joao Martins
2021-05-05 22:43 ` Dan Williams
2021-05-06 10:27 ` Joao Martins
2021-05-06 18:36 ` Joao Martins
2021-03-25 23:09 ` [PATCH v1 07/11] mm/sparse-vmemmap: populate compound pagemaps Joao Martins
2021-05-06 1:18 ` Dan Williams
2021-05-06 11:01 ` Joao Martins
2021-05-10 19:19 ` Dan Williams
2021-05-13 18:45 ` Joao Martins
2021-06-16 15:05 ` Joao Martins
2021-06-16 23:35 ` Dan Williams
2021-03-25 23:09 ` [PATCH v1 08/11] mm/sparse-vmemmap: use hugepages for PUD " Joao Martins
2021-06-01 19:30 ` Dan Williams
2021-06-07 12:02 ` Joao Martins
2021-06-07 19:47 ` Dan Williams
2021-03-25 23:09 ` [PATCH v1 09/11] mm/page_alloc: reuse tail struct pages for " Joao Martins
2021-06-01 23:35 ` Dan Williams
2021-06-07 13:48 ` Joao Martins
2021-06-07 19:32 ` Dan Williams
2021-06-14 18:41 ` Joao Martins
2021-06-14 23:07 ` Dan Williams
2021-03-25 23:09 ` [PATCH v1 10/11] device-dax: compound pagemap support Joao Martins
2021-06-02 0:36 ` Dan Williams
2021-06-07 13:59 ` Joao Martins
2021-03-25 23:09 ` [PATCH v1 11/11] mm/gup: grab head page refcount once for group of subpages Joao Martins
2021-06-02 1:05 ` Dan Williams
2021-06-07 15:21 ` Joao Martins
2021-06-07 19:22 ` Dan Williams
2021-04-01 9:38 ` [PATCH v1 00/11] mm, sparse-vmemmap: Introduce compound pagemaps Joao Martins
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