Commit 01cefaef authored by Jiang Liu's avatar Jiang Liu Committed by Linus Torvalds

mm: provide more accurate estimation of pages occupied by memmap

If SPARSEMEM is enabled, it won't build page structures for non-existing
pages (holes) within a zone, so provide a more accurate estimation of
pages occupied by memmap if there are bigger holes within the zone.

And pages for highmem zones' memmap will be allocated from lowmem, so
charge nr_kernel_pages for that.

[akpm@linux-foundation.org: mark calc_memmap_size __paging_init]
Signed-off-by: default avatarJiang Liu <jiang.liu@huawei.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Maciej Rutecki <maciej.rutecki@gmail.com>
Cc: Chris Clayton <chris2553@googlemail.com>
Cc: "Rafael J . Wysocki" <rjw@sisk.pl>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Tested-by: default avatarJianguo Wu <wujianguo@huawei.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 02c0ab68
...@@ -4489,6 +4489,26 @@ void __init set_pageblock_order(void) ...@@ -4489,6 +4489,26 @@ void __init set_pageblock_order(void)
#endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */ #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
static unsigned long __paginginit calc_memmap_size(unsigned long spanned_pages,
unsigned long present_pages)
{
unsigned long pages = spanned_pages;
/*
* Provide a more accurate estimation if there are holes within
* the zone and SPARSEMEM is in use. If there are holes within the
* zone, each populated memory region may cost us one or two extra
* memmap pages due to alignment because memmap pages for each
* populated regions may not naturally algined on page boundary.
* So the (present_pages >> 4) heuristic is a tradeoff for that.
*/
if (spanned_pages > present_pages + (present_pages >> 4) &&
IS_ENABLED(CONFIG_SPARSEMEM))
pages = present_pages;
return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT;
}
/* /*
* Set up the zone data structures: * Set up the zone data structures:
* - mark all pages reserved * - mark all pages reserved
...@@ -4523,8 +4543,7 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat, ...@@ -4523,8 +4543,7 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
* is used by this zone for memmap. This affects the watermark * is used by this zone for memmap. This affects the watermark
* and per-cpu initialisations * and per-cpu initialisations
*/ */
memmap_pages = memmap_pages = calc_memmap_size(size, realsize);
PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT;
if (freesize >= memmap_pages) { if (freesize >= memmap_pages) {
freesize -= memmap_pages; freesize -= memmap_pages;
if (memmap_pages) if (memmap_pages)
...@@ -4545,6 +4564,9 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat, ...@@ -4545,6 +4564,9 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
if (!is_highmem_idx(j)) if (!is_highmem_idx(j))
nr_kernel_pages += freesize; nr_kernel_pages += freesize;
/* Charge for highmem memmap if there are enough kernel pages */
else if (nr_kernel_pages > memmap_pages * 2)
nr_kernel_pages -= memmap_pages;
nr_all_pages += freesize; nr_all_pages += freesize;
zone->spanned_pages = size; zone->spanned_pages = size;
......
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