From: Dan Williams <dan.j.williams@intel.com>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: Linux MM <linux-mm@kvack.org>,
Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
Matthew Wilcox <willy@infradead.org>,
Jason Gunthorpe <jgg@ziepe.ca>,
John Hubbard <jhubbard@nvidia.com>,
Jane Chu <jane.chu@oracle.com>,
Muchun Song <songmuchun@bytedance.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jonathan Corbet <corbet@lwn.net>,
Linux NVDIMM <nvdimm@lists.linux.dev>,
Linux Doc Mailing List <linux-doc@vger.kernel.org>
Subject: Re: [PATCH v3 09/14] mm/page_alloc: reuse tail struct pages for compound pagemaps
Date: Wed, 28 Jul 2021 00:28:25 -0700 [thread overview]
Message-ID: <CAPcyv4gDndA612+1BKZcR518K_Rt3Q1gWpqK24KOqvoFp_PNGg@mail.gmail.com> (raw)
In-Reply-To: <20210714193542.21857-10-joao.m.martins@oracle.com>
On Wed, Jul 14, 2021 at 12:36 PM Joao Martins <joao.m.martins@oracle.com> wrote:
>
> Currently memmap_init_zone_device() ends up initializing 32768 pages
> when it only needs to initialize 128 given tail page reuse. That
> number is worse with 1GB compound page geometries, 262144 instead of
> 128. Update memmap_init_zone_device() to skip redundant
> initialization, detailed below.
>
> When a pgmap @geometry is set, all pages are mapped at a given huge page
> alignment and use compound pages to describe them as opposed to a
> struct per 4K.
>
> With @geometry > PAGE_SIZE and when struct pages are stored in ram
> (!altmap) most tail pages are reused. Consequently, the amount of unique
> struct pages is a lot smaller that the total amount of struct pages
> being mapped.
>
> The altmap path is left alone since it does not support memory savings
> based on compound pagemap geometries.
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
> mm/page_alloc.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 188cb5f8c308..96975edac0a8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6600,11 +6600,23 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
> static void __ref memmap_init_compound(struct page *page, unsigned long pfn,
> unsigned long zone_idx, int nid,
> struct dev_pagemap *pgmap,
> + struct vmem_altmap *altmap,
> unsigned long nr_pages)
> {
> unsigned int order_align = order_base_2(nr_pages);
> unsigned long i;
>
> + /*
> + * With compound page geometry and when struct pages are stored in ram
> + * (!altmap) most tail pages are reused. Consequently, the amount of
> + * unique struct pages to initialize is a lot smaller that the total
> + * amount of struct pages being mapped.
> + * See vmemmap_populate_compound_pages().
> + */
> + if (!altmap)
> + nr_pages = min_t(unsigned long, nr_pages,
What's the scenario where nr_pages is < 128? Shouldn't alignment
already be guaranteed?
> + 2 * (PAGE_SIZE/sizeof(struct page)));
> +
> __SetPageHead(page);
>
> for (i = 1; i < nr_pages; i++) {
> @@ -6657,7 +6669,7 @@ void __ref memmap_init_zone_device(struct zone *zone,
> continue;
>
> memmap_init_compound(page, pfn, zone_idx, nid, pgmap,
> - pfns_per_compound);
> + altmap, pfns_per_compound);
This feels odd, memmap_init_compound() doesn't really care about
altmap, what do you think about explicitly calculating the parameters
that memmap_init_compound() needs and passing them in?
Not a strong requirement to change, but take another look at let me know.
> }
>
> pr_info("%s initialised %lu pages in %ums\n", __func__,
> --
> 2.17.1
>
next prev parent reply other threads:[~2021-07-28 7:28 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-14 19:35 [PATCH v3 00/14] mm, sparse-vmemmap: Introduce compound pagemaps Joao Martins
2021-07-14 19:35 ` [PATCH v3 01/14] memory-failure: fetch compound_head after pgmap_pfn_valid() Joao Martins
2021-07-15 0:17 ` Dan Williams
2021-07-15 2:51 ` [External] " Muchun Song
2021-07-15 6:40 ` Christoph Hellwig
2021-07-15 9:19 ` Muchun Song
2021-07-15 13:17 ` Joao Martins
2021-07-14 19:35 ` [PATCH v3 02/14] mm/page_alloc: split prep_compound_page into head and tail subparts Joao Martins
2021-07-15 0:19 ` Dan Williams
2021-07-15 2:53 ` [External] " Muchun Song
2021-07-15 13:17 ` Joao Martins
2021-07-14 19:35 ` [PATCH v3 03/14] mm/page_alloc: refactor memmap_init_zone_device() page init Joao Martins
2021-07-15 0:20 ` Dan Williams
2021-07-14 19:35 ` [PATCH v3 04/14] mm/memremap: add ZONE_DEVICE support for compound pages Joao Martins
2021-07-15 1:08 ` Dan Williams
2021-07-15 12:52 ` Joao Martins
2021-07-15 13:06 ` Joao Martins
2021-07-15 19:48 ` Dan Williams
2021-07-30 16:13 ` Joao Martins
2021-07-22 0:38 ` Jane Chu
2021-07-22 10:56 ` Joao Martins
2021-07-15 12:59 ` Christoph Hellwig
2021-07-15 13:15 ` Joao Martins
2021-07-15 6:48 ` Christoph Hellwig
2021-07-15 13:15 ` Joao Martins
2021-07-14 19:35 ` [PATCH v3 05/14] mm/sparse-vmemmap: add a pgmap argument to section activation Joao Martins
2021-07-28 5:56 ` Dan Williams
2021-07-28 9:43 ` Joao Martins
2021-07-14 19:35 ` [PATCH v3 06/14] mm/sparse-vmemmap: refactor core of vmemmap_populate_basepages() to helper Joao Martins
2021-07-28 6:04 ` Dan Williams
2021-07-28 10:48 ` Joao Martins
2021-07-14 19:35 ` [PATCH v3 07/14] mm/hugetlb_vmemmap: move comment block to Documentation/vm Joao Martins
2021-07-15 2:47 ` [External] " Muchun Song
2021-07-15 13:16 ` Joao Martins
2021-07-28 6:09 ` Dan Williams
2021-07-14 19:35 ` [PATCH v3 08/14] mm/sparse-vmemmap: populate compound pagemaps Joao Martins
2021-07-28 6:55 ` Dan Williams
2021-07-28 15:35 ` Joao Martins
2021-07-28 18:03 ` Dan Williams
2021-07-28 18:54 ` Joao Martins
2021-07-28 20:04 ` Joao Martins
2021-07-14 19:35 ` [PATCH v3 09/14] mm/page_alloc: reuse tail struct pages for " Joao Martins
2021-07-28 7:28 ` Dan Williams [this message]
2021-07-28 15:56 ` Joao Martins
2021-07-28 16:08 ` Dan Williams
2021-07-28 16:12 ` Joao Martins
2021-07-14 19:35 ` [PATCH v3 10/14] device-dax: use ALIGN() for determining pgoff Joao Martins
2021-07-28 7:29 ` Dan Williams
2021-07-28 15:56 ` Joao Martins
2021-07-14 19:35 ` [PATCH v3 11/14] device-dax: ensure dev_dax->pgmap is valid for dynamic devices Joao Martins
2021-07-28 7:30 ` Dan Williams
2021-07-28 15:56 ` Joao Martins
2021-08-06 12:28 ` Joao Martins
2021-07-14 19:35 ` [PATCH v3 12/14] device-dax: compound pagemap support Joao Martins
2021-07-14 23:36 ` Dan Williams
2021-07-15 12:00 ` Joao Martins
2021-07-27 23:51 ` Dan Williams
2021-07-28 9:36 ` Joao Martins
2021-07-28 18:51 ` Dan Williams
2021-07-28 18:59 ` Joao Martins
2021-07-28 19:03 ` Dan Williams
2021-07-14 19:35 ` [PATCH v3 13/14] mm/gup: grab head page refcount once for group of subpages Joao Martins
2021-07-28 19:55 ` Dan Williams
2021-07-28 20:07 ` Joao Martins
2021-07-28 20:23 ` Dan Williams
2021-08-25 19:10 ` Joao Martins
2021-08-25 19:15 ` Matthew Wilcox
2021-08-25 19:26 ` Joao Martins
2021-07-14 19:35 ` [PATCH v3 14/14] mm/sparse-vmemmap: improve memory savings for compound pud geometry Joao Martins
2021-07-28 20:03 ` Dan Williams
2021-07-28 20:08 ` Joao Martins
2021-07-14 21:48 ` [PATCH v3 00/14] mm, sparse-vmemmap: Introduce compound pagemaps Andrew Morton
2021-07-14 23:47 ` Dan Williams
2021-07-22 2:24 ` Matthew Wilcox
2021-07-22 10:53 ` Joao Martins
2021-07-27 23:23 ` Dan Williams
2021-08-02 10:40 ` Joao Martins
2021-08-02 14:06 ` Dan Williams
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