Re: [PATCH v2 2/9] mm/vmstat: show start_pfn when zone spans pages

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On 29.09.22 00:32, Doug Berger wrote:
A zone that overlaps with another zone may span a range of pages
that are not present. In this case, displaying the start_pfn of
the zone allows the zone page range to be identified.


I don't understand the intention here.

"/* If unpopulated, no other information is useful */"

Why would the start pfn be of any use here?

What is the user visible impact without that change?

Signed-off-by: Doug Berger <opendmb@xxxxxxxxx>
---
  mm/vmstat.c | 5 +++++
  1 file changed, 5 insertions(+)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 90af9a8572f5..e2f19f2b7615 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1717,6 +1717,11 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
/* If unpopulated, no other information is useful */
  	if (!populated_zone(zone)) {
+		/* Show start_pfn for empty overlapped zones */
+		if (zone->spanned_pages)
+			seq_printf(m,
+				   "\n  start_pfn:           %lu",
+				   zone->zone_start_pfn);
  		seq_putc(m, '\n');
  		return;
  	}
--
Thanks,

David / dhildenb





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