On Wed, Jan 27, 2021 at 11:18:13AM +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 (e.g., like
ZONE_MOVABLE) - even after some of these pages might already have been
allocated.
My knowledge of CMA tends to be quite low, actually I though that CMA
was somehow tied to ZONE_MOVABLE.
I see how tracking CMA pages per zona might give you a clue, but what do
you mean by "might behave differently - even after some of these pages might
already have been allocated"
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.
Note: Track/print that information even without CONFIG_CMA, similar to
"nr_free_cma" in /proc/zoneinfo. This is different to /proc/meminfo -
maybe we want to make that consistent in the future (however, changing
/proc/zoneinfo output might uglify the code a bit).
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
include/linux/mmzone.h | 4 ++++
mm/page_alloc.c | 1 +
mm/vmstat.c | 6 ++++--
3 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index ae588b2f87ef..3bc18c9976fd 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 +530,7 @@ struct zone {
atomic_long_t managed_pages;
unsigned long spanned_pages;
unsigned long present_pages;
+ unsigned long cma_pages;
I see that NR_FREE_CMA_PAGES is there even without CONFIG_CMA, as you
said, but I am not sure about adding size to a zone unconditionally.
I mean, it is not terrible as IIRC, the maximum MAX_NUMNODES can get
is 1024, and on x86_64 that would be (1024 * 4 zones) * 8 = 32K.
So not a big deal, but still.
Besides following NR_FREE_CMA_PAGES, is there any reason for not doing:
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 1e22d96734e0..2d8a830d168d 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -436,6 +436,9 @@ struct zone {
unsigned long managed_pages;
unsigned long spanned_pages;
unsigned long present_pages;
+#ifdef CONFIG_CMA
+ unsigned long cma_pages;
+#endif
const char *name;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 8ba0870ecddd..5757df4bfd45 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1559,13 +1559,15 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
"\n spanned %lu"
"\n present %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->managed_pages,
+ IS_ENABLED(CONFIG_CMA) ? zone->cma_pages : 0);
seq_printf(m,
"\n protection: (%ld",
I do not see it that ugly, but just my taste.