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0002-linux-dmjordan.git-018908fd0f9a56156bc34bc86781a7877c3d4d20.patch
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0002-linux-dmjordan.git-018908fd0f9a56156bc34bc86781a7877c3d4d20.patch
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From 018908fd0f9a56156bc34bc86781a7877c3d4d20 Mon Sep 17 00:00:00 2001
From: Pavel Tatashin <[email protected]>
Date: Wed, 29 Apr 2020 04:02:01 +0000
Subject: [PATCH] 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/[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 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
Link: http://lkml.kernel.org/r/[email protected]
Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages")
Reported-by: Shile Zhang <[email protected]>
Signed-off-by: Pavel Tatashin <[email protected]>
Reviewed-by: Daniel Jordan <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Reviewed-by: David Hildenbrand <[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+]
Signed-off-by: Andrew Morton <[email protected]>
---
include/linux/mmzone.h | 2 ++
mm/page_alloc.c | 20 +++++++-------------
2 files changed, 9 insertions(+), 13 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 462f687..c5bdf55 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -721,6 +721,8 @@ 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
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e8ff6a1..4a60f24 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1790,6 +1790,13 @@ 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;
@@ -1812,8 +1819,6 @@ 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));
@@ -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.
*/
--
1.7.4.1