On Fri, Jan 29, 2021 at 12:34:51PM +0100, David Hildenbrand wrote:
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.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <redacted>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Wei Yang <redacted>
3 more quoted lines
Looks good to me, I guess it is better to print it unconditionally
so the layout does not change.
Reviewed-by: Oscar Salvador <osalvador@suse.de>
thanks
quoted hunk
---
The third time is the charm.
v2 -> v3:
- Print even without CONFIG_CMA. Use zone_cma_pages().
- Adjust patch description
- Dropped Oscar's RB due to the changes
v1 -> v2:
- Print/track only with CONFIG_CMA
- Extend patch description
---
include/linux/mmzone.h | 15 +++++++++++++++
mm/page_alloc.c | 1 +
mm/vmstat.c | 6 ++++--
3 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index ae588b2f87ef..caafd5e37080 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -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
58 more quoted lines
--
Oscar Salvador
SUSE L3