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mm: introduce new field "managed_pages" to struct zone

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Currently a zone's present_pages is calcuated as below, which is
inaccurate and may cause trouble to memory hotplug.

	spanned_pages - absent_pages - memmap_pages - dma_reserve.

During fixing bugs caused by inaccurate zone->present_pages, we found
zone->present_pages has been abused.  The field zone->present_pages may
have different meanings in different contexts:

1) pages existing in a zone.
2) pages managed by the buddy system.

For more discussions about the issue, please refer to:
  http://lkml.org/lkml/2012/11/5/866
  https://patchwork.kernel.org/patch/1346751/

This patchset tries to introduce a new field named "managed_pages" to
struct zone, which counts "pages managed by the buddy system".  And revert
zone->present_pages to count "physical pages existing in a zone", which
also keep in consistence with pgdat->node_present_pages.

We will set an initial value for zone->managed_pages in function
free_area_init_core() and will adjust it later if the initial value is
inaccurate.

For DMA/normal zones, the initial value is set to:

	(spanned_pages - absent_pages - memmap_pages - dma_reserve)

Later zone->managed_pages will be adjusted to the accurate value when the
bootmem allocator frees all free pages to the buddy system in function
free_all_bootmem_node() and free_all_bootmem().

The bootmem allocator doesn't touch highmem pages, so highmem zones'
managed_pages is set to the accurate value "spanned_pages - absent_pages"
in function free_area_init_core() and won't be updated anymore.

This patch also adds a new field "managed_pages" to /proc/zoneinfo
and sysrq showmem.

[[email protected]: small comment tweaks]
Signed-off-by: Jiang Liu <[email protected]>
Cc: Wen Congyang <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Maciej Rutecki <[email protected]>
Tested-by: Chris Clayton <[email protected]>
Cc: "Rafael J . Wysocki" <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Jianguo Wu <[email protected]>
Cc: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Jiang Liu 2012-12-12 13:52:12 -08:00 • committed by Linus Torvalds
commit 9feedc9d83
6 changed files with 121 additions and 23 deletions
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21
mm/bootmem.c
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@ -229,6 +229,22 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
return count;
}
static void reset_node_lowmem_managed_pages(pg_data_t *pgdat)
{
struct zone *z;
/*
* In free_area_init_core(), highmem zone's managed_pages is set to
* present_pages, and bootmem allocator doesn't allocate from highmem
* zones. So there's no need to recalculate managed_pages because all
* highmem pages will be managed by the buddy system. Here highmem
* zone also includes highmem movable zone.
*/
for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
if (!is_highmem(z))
z->managed_pages = 0;
}
/**
* free_all_bootmem_node - release a node's free pages to the buddy allocator
* @pgdat: node to be released
@ -238,6 +254,7 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
unsigned long __init free_all_bootmem_node(pg_data_t *pgdat)
{
register_page_bootmem_info_node(pgdat);
reset_node_lowmem_managed_pages(pgdat);
return free_all_bootmem_core(pgdat->bdata);
}
@ -250,6 +267,10 @@ unsigned long __init free_all_bootmem(void)
{
unsigned long total_pages = 0;
bootmem_data_t *bdata;
struct pglist_data *pgdat;
for_each_online_pgdat(pgdat)
reset_node_lowmem_managed_pages(pgdat);
list_for_each_entry(bdata, &bdata_list, list)
total_pages += free_all_bootmem_core(bdata);