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thp: make split_queue per-node
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Andrea Arcangeli suggested to make split queue per-node to improve
scalability.  Let's do it.

Signed-off-by: Kirill A. Shutemov <[email protected]>
Suggested-by: Andrea Arcangeli <[email protected]>
Reviewed-by: Andrea Arcangeli <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: "Aneesh Kumar K.V" <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Jerome Marchand <[email protected]>
Cc: Sasha Levin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@kiryl @torvalds
kiryl authored and torvalds committed Feb 3, 2016
1 parent 34229b2 commit a3d0a91
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Showing 3 changed files with 37 additions and 23 deletions.
6 changes: 6 additions & 0 deletions include/linux/mmzone.h
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Original file line number Diff line number Diff line change
Expand Up @@ -682,6 +682,12 @@ typedef struct pglist_data {
*/
unsigned long first_deferred_pfn;
#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
spinlock_t split_queue_lock;
struct list_head split_queue;
unsigned long split_queue_len;
#endif
} pg_data_t;

#define node_present_pages(nid) (NODE_DATA(nid)->node_present_pages)
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49 changes: 26 additions & 23 deletions mm/huge_memory.c
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Original file line number Diff line number Diff line change
Expand Up @@ -138,9 +138,6 @@ static struct khugepaged_scan khugepaged_scan = {
.mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
};

static DEFINE_SPINLOCK(split_queue_lock);
static LIST_HEAD(split_queue);
static unsigned long split_queue_len;
static struct shrinker deferred_split_shrinker;

static void set_recommended_min_free_kbytes(void)
Expand Down Expand Up @@ -3358,6 +3355,7 @@ int total_mapcount(struct page *page)
int split_huge_page_to_list(struct page *page, struct list_head *list)
{
struct page *head = compound_head(page);
struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
struct anon_vma *anon_vma;
int count, mapcount, ret;
bool mlocked;
Expand Down Expand Up @@ -3401,27 +3399,27 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
lru_add_drain();

/* Prevent deferred_split_scan() touching ->_count */
spin_lock_irqsave(&split_queue_lock, flags);
spin_lock_irqsave(&pgdata->split_queue_lock, flags);
count = page_count(head);
mapcount = total_mapcount(head);
if (!mapcount && count == 1) {
if (!list_empty(page_deferred_list(head))) {
split_queue_len--;
pgdata->split_queue_len--;
list_del(page_deferred_list(head));
}
spin_unlock_irqrestore(&split_queue_lock, flags);
spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
__split_huge_page(page, list);
ret = 0;
} else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
spin_unlock_irqrestore(&split_queue_lock, flags);
spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
pr_alert("total_mapcount: %u, page_count(): %u\n",
mapcount, count);
if (PageTail(page))
dump_page(head, NULL);
dump_page(page, "total_mapcount(head) > 0");
BUG();
} else {
spin_unlock_irqrestore(&split_queue_lock, flags);
spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
unfreeze_page(anon_vma, head);
ret = -EBUSY;
}
Expand All @@ -3436,52 +3434,56 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)

void free_transhuge_page(struct page *page)
{
struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
unsigned long flags;

spin_lock_irqsave(&split_queue_lock, flags);
spin_lock_irqsave(&pgdata->split_queue_lock, flags);
if (!list_empty(page_deferred_list(page))) {
split_queue_len--;
pgdata->split_queue_len--;
list_del(page_deferred_list(page));
}
spin_unlock_irqrestore(&split_queue_lock, flags);
spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
free_compound_page(page);
}

void deferred_split_huge_page(struct page *page)
{
struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
unsigned long flags;

VM_BUG_ON_PAGE(!PageTransHuge(page), page);

spin_lock_irqsave(&split_queue_lock, flags);
spin_lock_irqsave(&pgdata->split_queue_lock, flags);
if (list_empty(page_deferred_list(page))) {
list_add_tail(page_deferred_list(page), &split_queue);
split_queue_len++;
list_add_tail(page_deferred_list(page), &pgdata->split_queue);
pgdata->split_queue_len++;
}
spin_unlock_irqrestore(&split_queue_lock, flags);
spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
}

static unsigned long deferred_split_count(struct shrinker *shrink,
struct shrink_control *sc)
{
struct pglist_data *pgdata = NODE_DATA(sc->nid);
/*
* Split a page from split_queue will free up at least one page,
* at most HPAGE_PMD_NR - 1. We don't track exact number.
* Let's use HPAGE_PMD_NR / 2 as ballpark.
*/
return ACCESS_ONCE(split_queue_len) * HPAGE_PMD_NR / 2;
return ACCESS_ONCE(pgdata->split_queue_len) * HPAGE_PMD_NR / 2;
}

static unsigned long deferred_split_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
struct pglist_data *pgdata = NODE_DATA(sc->nid);
unsigned long flags;
LIST_HEAD(list), *pos, *next;
struct page *page;
int split = 0;

spin_lock_irqsave(&split_queue_lock, flags);
list_splice_init(&split_queue, &list);
spin_lock_irqsave(&pgdata->split_queue_lock, flags);
list_splice_init(&pgdata->split_queue, &list);

/* Take pin on all head pages to avoid freeing them under us */
list_for_each_safe(pos, next, &list) {
Expand All @@ -3490,10 +3492,10 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
/* race with put_compound_page() */
if (!get_page_unless_zero(page)) {
list_del_init(page_deferred_list(page));
split_queue_len--;
pgdata->split_queue_len--;
}
}
spin_unlock_irqrestore(&split_queue_lock, flags);
spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);

list_for_each_safe(pos, next, &list) {
page = list_entry((void *)pos, struct page, mapping);
Expand All @@ -3505,9 +3507,9 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
put_page(page);
}

spin_lock_irqsave(&split_queue_lock, flags);
list_splice_tail(&list, &split_queue);
spin_unlock_irqrestore(&split_queue_lock, flags);
spin_lock_irqsave(&pgdata->split_queue_lock, flags);
list_splice_tail(&list, &pgdata->split_queue);
spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);

return split * HPAGE_PMD_NR / 2;
}
Expand All @@ -3516,6 +3518,7 @@ static struct shrinker deferred_split_shrinker = {
.count_objects = deferred_split_count,
.scan_objects = deferred_split_scan,
.seeks = DEFAULT_SEEKS,
.flags = SHRINKER_NUMA_AWARE,
};

#ifdef CONFIG_DEBUG_FS
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5 changes: 5 additions & 0 deletions mm/page_alloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5209,6 +5209,11 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat)
spin_lock_init(&pgdat->numabalancing_migrate_lock);
pgdat->numabalancing_migrate_nr_pages = 0;
pgdat->numabalancing_migrate_next_window = jiffies;
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
spin_lock_init(&pgdat->split_queue_lock);
INIT_LIST_HEAD(&pgdat->split_queue);
pgdat->split_queue_len = 0;
#endif
init_waitqueue_head(&pgdat->kswapd_wait);
init_waitqueue_head(&pgdat->pfmemalloc_wait);
Expand Down

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