diff options
| author | Joao Martins <joao.m.martins@oracle.com> | 2022-04-28 23:16:16 -0700 |
|---|---|---|
| committer | akpm <akpm@linux-foundation.org> | 2022-04-28 23:16:16 -0700 |
| commit | 6fd3620b342861de9547ea01d28f664892ef51a1 (patch) | |
| tree | 07ea9306c6fee977cb55f748097dc6224eb47ae3 /mm/page_alloc.c | |
| parent | 4917f55b4ef963e2d2288fe4eb651728be8db406 (diff) | |
mm/page_alloc: reuse tail struct pages for compound devmaps
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 pages, 262144 instead of 128. Update
memmap_init_zone_device() to skip redundant initialization, detailed
below.
When a pgmap @vmemmap_shift 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 @vmemmap_shift > 0 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 than the total amount of struct pages being mapped.
The altmap path is left alone since it does not support memory savings
based on compound pages devmap.
Link: https://lkml.kernel.org/r/20220420155310.9712-6-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 298c7691fb1d..e80858f5c2ab 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6596,6 +6596,21 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn, } } +/* + * With compound page geometry and when struct pages are stored in ram 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. This is a paired / mild layering violation with explicit knowledge + * of how the sparse_vmemmap internals handle compound pages in the lack + * of an altmap. See vmemmap_populate_compound_pages(). + */ +static inline unsigned long compound_nr_pages(struct vmem_altmap *altmap, + unsigned long nr_pages) +{ + return is_power_of_2(sizeof(struct page)) && + !altmap ? 2 * (PAGE_SIZE / sizeof(struct page)) : nr_pages; +} + static void __ref memmap_init_compound(struct page *head, unsigned long head_pfn, unsigned long zone_idx, int nid, @@ -6660,7 +6675,7 @@ void __ref memmap_init_zone_device(struct zone *zone, continue; memmap_init_compound(page, pfn, zone_idx, nid, pgmap, - pfns_per_compound); + compound_nr_pages(altmap, pfns_per_compound)); } pr_info("%s initialised %lu pages in %ums\n", __func__, |