[049/131] mm/pagealloc.c: call touch_nmi_watchdog() on max order boundaries in deferred init

Commit Message

Andrew Morton June 3, 2020, 10:59 p.m. UTC

From: Daniel Jordan <[e-mail]>
Subject: mm/pagealloc.c: call touch_nmi_watchdog() on max order boundaries in deferred init

Patch series "initialize deferred pages with interrupts enabled", v4.

Keep interrupts enabled during deferred page initialization in order to
make code more modular and allow jiffies to update.

Original approach, and discussion can be found here:
 http://lkml.kernel.org/r/[e-mail]


This patch (of 3):

deferred_init_memmap() disables interrupts the entire time, so it calls
touch_nmi_watchdog() periodically to avoid soft lockup splats.  Soon it
will run with interrupts enabled, at which point cond_resched() should be
used instead.

deferred_grow_zone() makes the same watchdog calls through code shared
with deferred init but will continue to run with interrupts disabled, so
it can't call cond_resched().

Pull the watchdog calls up to these two places to allow the first to be
changed later, independently of the second.  The frequency reduces from
twice per pageblock (init and free) to once per max order block.

Link: http://lkml.kernel.org/r/[e-mail]
Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages")
Signed-off-by: Daniel Jordan <[e-mail]>
Signed-off-by: Pavel Tatashin <[e-mail]>
Reviewed-by: David Hildenbrand <[e-mail]>
Acked-by: Michal Hocko <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Shile Zhang <[e-mail]>
Cc: Kirill Tkhai <[e-mail]>
Cc: James Morris <[e-mail]>
Cc: Sasha Levin <[e-mail]>
Cc: Yiqian Wei <[e-mail]>
Cc: <[e-mail]>	[4.17+]
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/page_alloc.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Patch

--- a/mm/page_alloc.c~mm-call-touch_nmi_watchdog-on-max-order-boundaries-in-deferred-init
+++ a/mm/page_alloc.c
@@ -1693,7 +1693,6 @@  static void __init deferred_free_pages(u
 		} else if (!(pfn & nr_pgmask)) {
 			deferred_free_range(pfn - nr_free, nr_free);
 			nr_free = 1;
-			touch_nmi_watchdog();
 		} else {
 			nr_free++;
 		}
@@ -1723,7 +1722,6 @@  static unsigned long  __init deferred_in
 			continue;
 		} else if (!page || !(pfn & nr_pgmask)) {
 			page = pfn_to_page(pfn);
-			touch_nmi_watchdog();
 		} else {
 			page++;
 		}
@@ -1863,8 +1861,10 @@  static int __init deferred_init_memmap(v
 	 * that we can avoid introducing any issues with the buddy
 	 * allocator.
 	 */
-	while (spfn < epfn)
+	while (spfn < epfn) {
 		nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
+		touch_nmi_watchdog();
+	}
 zone_empty:
 	pgdat_resize_unlock(pgdat, &flags);
 
@@ -1948,6 +1948,7 @@  deferred_grow_zone(struct zone *zone, un
 		first_deferred_pfn = spfn;
 
 		nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
+		touch_nmi_watchdog();
 
 		/* We should only stop along section boundaries */
 		if ((first_deferred_pfn ^ spfn) < PAGES_PER_SECTION)