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mm/page_alloc: count CMA pages per zone and print them in /proc/zoneinfo

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Let's count the number of CMA pages per zone and print them in
/proc/zoneinfo.

Having access to the total number of CMA pages per zone is helpful for
debugging purposes to know where exactly the CMA pages ended up, and to
figure out how many pages of a zone might behave differently, even after
some of these pages might already have been allocated.

As one example, CMA pages part of a kernel zone cannot be used for
ordinary kernel allocations but instead behave more like ZONE_MOVABLE.

For now, we are only able to get the global nr+free cma pages from
/proc/meminfo and the free cma pages per zone from /proc/zoneinfo.

Example after this patch when booting a 6 GiB QEMU VM with
"hugetlb_cma=2G":
  # cat /proc/zoneinfo | grep cma
          cma      0
        nr_free_cma  0
          cma      0
        nr_free_cma  0
          cma      524288
        nr_free_cma  493016
          cma      0
          cma      0
  # cat /proc/meminfo | grep Cma
  CmaTotal:        2097152 kB
  CmaFree:         1972064 kB

Note: We print even without CONFIG_CMA, just like "nr_free_cma"; this way,
      one can be sure when spotting "cma 0", that there are definetly no
      CMA pages located in a zone.

[david@redhat.com: v2]
  Link: https://lkml.kernel.org/r/20210128164533.18566-1-david@redhat.com
[david@redhat.com: v3]
  Link: https://lkml.kernel.org/r/20210129113451.22085-1-david@redhat.com

Link: https://lkml.kernel.org/r/20210127101813.6370-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2021-02-25 17:16:40 -08:00 committed by Linus Torvalds
parent 072355c1cf
commit 3c381db1fa
3 changed files with 20 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

15
include/linux/mmzone.h
View file

@ -503,6 +503,9 @@ struct zone {
* bootmem allocator):
* managed_pages = present_pages - reserved_pages;
*
* cma pages is present pages that are assigned for CMA use
* (MIGRATE_CMA).
*
* So present_pages may be used by memory hotplug or memory power
* management logic to figure out unmanaged pages by checking
* (present_pages - managed_pages). And managed_pages should be used
@ -527,6 +530,9 @@ struct zone {
atomic_long_t managed_pages;
unsigned long spanned_pages;
unsigned long present_pages;
#ifdef CONFIG_CMA
unsigned long cma_pages;
#endif
const char *name;
@ -624,6 +630,15 @@ static inline unsigned long zone_managed_pages(struct zone *zone)
return (unsigned long)atomic_long_read(&zone->managed_pages);
}
static inline unsigned long zone_cma_pages(struct zone *zone)
{
#ifdef CONFIG_CMA
return zone->cma_pages;
#else
return 0;
#endif
}
static inline unsigned long zone_end_pfn(const struct zone *zone)
{
return zone->zone_start_pfn + zone->spanned_pages;

1
mm/page_alloc.c
View file

@ -2168,6 +2168,7 @@ void __init init_cma_reserved_pageblock(struct page *page)
}
adjust_managed_page_count(page, pageblock_nr_pages);
page_zone(page)->cma_pages += pageblock_nr_pages;
}
#endif

6
mm/vmstat.c
View file

@ -1637,14 +1637,16 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
"\n high %lu"
"\n spanned %lu"
"\n present %lu"
"\n managed %lu",
"\n managed %lu"
"\n cma %lu",
zone_page_state(zone, NR_FREE_PAGES),
min_wmark_pages(zone),
low_wmark_pages(zone),
high_wmark_pages(zone),
zone->spanned_pages,
zone->present_pages,
zone_managed_pages(zone));
zone_managed_pages(zone),
zone_cma_pages(zone));
seq_printf(m,
"\n protection: (%ld",