[050/131] mm: initialize deferred pages with interrupts enabled
diff mbox series

Message ID 20200603225924.kDWBwWWfU%akpm@linux-foundation.org
State New
Headers show
  • [001/131] mm/slub: fix a memory leak in sysfs_slab_add()
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Commit Message

Andrew Morton June 3, 2020, 10:59 p.m. UTC
From: Pavel Tatashin <pasha.tatashin@soleen.com>
Subject: mm: initialize deferred pages with interrupts enabled

Initializing struct pages is a long task and keeping interrupts disabled
for the duration of this operation introduces a number of problems.

1. jiffies are not updated for long period of time, and thus incorrect time
   is reported. See proposed solution and discussion here:
2. It prevents farther improving deferred page initialization by allowing
   intra-node multi-threading.

We are keeping interrupts disabled to solve a rather theoretical problem
that was never observed in real world (See 3a2d7fa8a3d5).

Let's keep interrupts enabled. In case we ever encounter a scenario where
an interrupt thread wants to allocate large amount of memory this early in
boot we can deal with that by growing zone (see deferred_grow_zone()) by
the needed amount before starting deferred_init_memmap() threads.

[    1.232459] node 0 initialised, 12058412 pages in 1ms

[    1.632580] node 0 initialised, 12051227 pages in 436ms

Link: http://lkml.kernel.org/r/20200403140952.17177-3-pasha.tatashin@soleen.com
Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages")
Reported-by: Shile Zhang <shile.zhang@linux.alibaba.com>
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Yiqian Wei <yiwei@redhat.com>
Cc: <stable@vger.kernel.org>	[4.17+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

 include/linux/mmzone.h |    2 ++
 mm/page_alloc.c        |   20 +++++++-------------
 2 files changed, 9 insertions(+), 13 deletions(-)

diff mbox series

--- a/include/linux/mmzone.h~mm-initialize-deferred-pages-with-interrupts-enabled
+++ a/include/linux/mmzone.h
@@ -680,6 +680,8 @@  typedef struct pglist_data {
 	 * Must be held any time you expect node_start_pfn,
 	 * node_present_pages, node_spanned_pages or nr_zones to stay constant.
+	 * Also synchronizes pgdat->first_deferred_pfn during deferred page
+	 * init.
 	 * pgdat_resize_lock() and pgdat_resize_unlock() are provided to
 	 * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG
--- a/mm/page_alloc.c~mm-initialize-deferred-pages-with-interrupts-enabled
+++ a/mm/page_alloc.c
@@ -1844,6 +1844,13 @@  static int __init deferred_init_memmap(v
 	BUG_ON(pgdat->first_deferred_pfn > pgdat_end_pfn(pgdat));
 	pgdat->first_deferred_pfn = ULONG_MAX;
+	/*
+	 * Once we unlock here, the zone cannot be grown anymore, thus if an
+	 * interrupt thread must allocate this early in boot, zone must be
+	 * pre-grown prior to start of deferred page initialization.
+	 */
+	pgdat_resize_unlock(pgdat, &flags);
 	/* Only the highest zone is deferred so find it */
 	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
 		zone = pgdat->node_zones + zid;
@@ -1866,8 +1873,6 @@  static int __init deferred_init_memmap(v
-	pgdat_resize_unlock(pgdat, &flags);
 	/* Sanity check that the next zone really is unpopulated */
 	WARN_ON(++zid < MAX_NR_ZONES && populated_zone(++zone));
@@ -1910,17 +1915,6 @@  deferred_grow_zone(struct zone *zone, un
 	pgdat_resize_lock(pgdat, &flags);
-	 * If deferred pages have been initialized while we were waiting for
-	 * the lock, return true, as the zone was grown.  The caller will retry
-	 * this zone.  We won't return to this function since the caller also
-	 * has this static branch.
-	 */
-	if (!static_branch_unlikely(&deferred_pages)) {
-		pgdat_resize_unlock(pgdat, &flags);
-		return true;
-	}
-	/*
 	 * If someone grew this zone while we were waiting for spinlock, return
 	 * true, as there might be enough pages already.