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mm: initialize deferred pages with interrupts enabled

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commit 3d060856adfc59afb9d029c233141334cfaba418 upstream.

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/[email protected]
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 3a2d7fa8a3).

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: 3a2d7fa8a3 ("mm: disable interrupts while initializing deferred pages")
Reported-by: Shile Zhang <[email protected]>
Signed-off-by: Pavel Tatashin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Daniel Jordan <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: James Morris <[email protected]>
Cc: Kirill Tkhai <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Yiqian Wei <[email protected]>
Cc: <[email protected]>	[4.17+]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Pavel Tatashin 2020-06-03 15:59:24 -07:00 • committed by Greg Kroah-Hartman
commit c388f173ed
2 changed files with 9 additions and 13 deletions
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20
mm/page_alloc.c
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@ -1793,6 +1793,13 @@ 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;
@ -1813,8 +1820,6 @@ static int __init deferred_init_memmap(void *data)
while (spfn < epfn)
nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
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));
@ -1856,17 +1861,6 @@ 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.