mm: initialize deferred pages with interrupts enabled
commit3d060856ad
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/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 (See3a2d7fa8a3
). 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 <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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -709,6 +709,8 @@ typedef struct pglist_data {
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/*
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* Must be held any time you expect node_start_pfn,
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* node_present_pages, node_spanned_pages or nr_zones to stay constant.
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* Also synchronizes pgdat->first_deferred_pfn during deferred page
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* init.
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*
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* pgdat_resize_lock() and pgdat_resize_unlock() are provided to
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* manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG
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@ -1793,6 +1793,13 @@ static int __init deferred_init_memmap(void *data)
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BUG_ON(pgdat->first_deferred_pfn > pgdat_end_pfn(pgdat));
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pgdat->first_deferred_pfn = ULONG_MAX;
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/*
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* Once we unlock here, the zone cannot be grown anymore, thus if an
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* interrupt thread must allocate this early in boot, zone must be
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* pre-grown prior to start of deferred page initialization.
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*/
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pgdat_resize_unlock(pgdat, &flags);
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/* Only the highest zone is deferred so find it */
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for (zid = 0; zid < MAX_NR_ZONES; zid++) {
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zone = pgdat->node_zones + zid;
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@ -1813,8 +1820,6 @@ static int __init deferred_init_memmap(void *data)
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while (spfn < epfn)
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nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn);
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zone_empty:
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pgdat_resize_unlock(pgdat, &flags);
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/* Sanity check that the next zone really is unpopulated */
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WARN_ON(++zid < MAX_NR_ZONES && populated_zone(++zone));
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@ -1856,17 +1861,6 @@ deferred_grow_zone(struct zone *zone, unsigned int order)
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pgdat_resize_lock(pgdat, &flags);
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/*
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* If deferred pages have been initialized while we were waiting for
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* the lock, return true, as the zone was grown. The caller will retry
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* this zone. We won't return to this function since the caller also
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* has this static branch.
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*/
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if (!static_branch_unlikely(&deferred_pages)) {
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pgdat_resize_unlock(pgdat, &flags);
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return true;
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}
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/*
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* If someone grew this zone while we were waiting for spinlock, return
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* true, as there might be enough pages already.
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