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From: Joao Martins <joao.m.martins@oracle.com>
To: linux-mm@kvack.org
Cc: Dan Williams <dan.j.williams@intel.com>,
	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>,
	nvdimm@lists.linux.dev, linux-doc@vger.kernel.org,
	Joao Martins <joao.m.martins@oracle.com>
Subject: [PATCH v3 09/14] mm/page_alloc: reuse tail struct pages for compound pagemaps
Date: Wed, 14 Jul 2021 20:35:37 +0100	[thread overview]
Message-ID: <20210714193542.21857-10-joao.m.martins@oracle.com> (raw)
In-Reply-To: <20210714193542.21857-1-joao.m.martins@oracle.com>

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,
+				 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);
 	}
 
 	pr_info("%s initialised %lu pages in %ums\n", __func__,
-- 
2.17.1


  parent reply	other threads:[~2021-07-14 19:36 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 " 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 ` Joao Martins [this message]
2021-07-28  7:28   ` [PATCH v3 09/14] mm/page_alloc: reuse tail struct pages for " Dan Williams
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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