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authorPavel Tatashin <pasha.tatashin@soleen.com>2020-06-03 15:59:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-03 20:09:45 -0700
commit3d060856adfc59afb9d029c233141334cfaba418 (patch)
tree898594e5faba111c53a0d5fedb5d5476634230bb /mm/page_alloc.c
parent117003c32771df617acf66e140fbdbdeb0ac71f5 (diff)
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: lkml/20200311123848.118638-1-shile.zhang@linux.alibaba.com 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. Before: [ 1.232459] node 0 initialised, 12058412 pages in 1ms After: [ 1.632580] node 0 initialised, 12051227 pages in 436ms 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com> Reviewed-by: David Hildenbrand <david@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> 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+] Link: http://lkml.kernel.org/r/20200403140952.17177-3-pasha.tatashin@soleen.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c20
1 files changed, 7 insertions, 13 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 148cf9a73f0b..c75561a3f144 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1844,6 +1844,13 @@ static int __init deferred_init_memmap(void *data)
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(void *data)
touch_nmi_watchdog();
}
zone_empty:
- 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, unsigned int order)
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.
*/