On Tue, 24 Mar 2020, Baoquan He wrote:
> This moving makes the layout of /proc/zoneinfo more sensible. And there
> are 4 zones at most currently, it doesn't need to scroll down much to get
> to the 1st populated zone, even though the 1st populated zone is MOVABLE
> zone.
>
Doesn't this introduce risk that it will break existing parsers of
/proc/zoneinfo in subtle ways?
In some cases /proc/zoneinfo is a tricky file to correctly parse because
you have to rely on the existing order in which it is printed to determine
which zone is being described. We need to print zones even with unmanaged
pages, for instance, otherwise userspace may be unaware of which zones are
supported and what order they are in. That's important to be able to
construct the proper string to use when writing vm.lowmem_reserve_ratio.
I'd prefer not changing the order of /proc/zoneinfo if it can be avoided
just because the risk outweighs the reward that we may break some
initscript parsers.
> Node 2, per-node stats
> nr_inactive_anon 48
> nr_active_anon 15454
> ...
> nr_foll_pin_acquired 0
> nr_foll_pin_released 0
> Node 2, zone DMA
> pages free 0
> min 0
> low 0
> high 0
> spanned 0
> present 0
> managed 0
> Node 2, zone DMA32
> pages free 0
> min 0
> low 0
> high 0
> spanned 0
> present 0
> managed 0
> Node 2, zone Normal
> pages free 0
> min 0
> low 0
> high 0
> spanned 0
> present 0
> managed 0
> Node 2, zone Movable
> pages free 196346
> min 3540
> ...
> managed 262144
>
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
> ---
> mm/vmstat.c | 18 +++++++++++-------
> 1 file changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 6fd1407f4632..4bbf9be786da 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1567,13 +1567,6 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
> {
> int i;
> seq_printf(m, "Node %d, zone %8s", pgdat->node_id, zone->name);
> - if (is_zone_first_populated(pgdat, zone)) {
> - seq_printf(m, "\n per-node stats");
> - for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
> - seq_printf(m, "\n %-12s %lu", node_stat_name(i),
> - node_page_state(pgdat, i));
> - }
> - }
> seq_printf(m,
> "\n pages free %lu"
> "\n min %lu"
> @@ -1648,7 +1641,18 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
> */
> static int zoneinfo_show(struct seq_file *m, void *arg)
> {
> + int i;
> pg_data_t *pgdat = (pg_data_t *)arg;
> +
> + if (node_state(pgdat->node_id, N_MEMORY)) {
> + seq_printf(m, "Node %d, per-node stats", pgdat->node_id);
> + for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
> + seq_printf(m, "\n %-12s %lu", node_stat_name(i),
> + node_page_state(pgdat, i));
> + }
> + seq_putc(m, '\n');
> + }
> +
> walk_zones_in_node(m, pgdat, false, false, zoneinfo_show_print);
> return 0;
> }
> --
> 2.17.2
>
>
>
