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thp: limit number of object to scan on deferred_split_scan() 

If we have a lot of pages in queue to be split, deferred_split_scan()
can spend unreasonable amount of time under spinlock with disabled
interrupts.

Let's cap number of pages to split on scan by sc->nr_to_scan.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2016-02-02 16:57:15 -08:00 committed by Linus Torvalds
parent cb8d68ec16
commit e3ae19535c
1 changed files with 6 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
mm/huge_memory.c
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@ -3478,17 +3478,19 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
int split = 0;
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) {
page = list_entry((void *)pos, struct page, mapping);
page = compound_head(page);
/* race with put_compound_page() */
if (!get_page_unless_zero(page)) {
if (get_page_unless_zero(page)) {
list_move(page_deferred_list(page), &list);
} else {
/* We lost race with put_compound_page() */
list_del_init(page_deferred_list(page));
pgdata->split_queue_len--;
}
if (!--sc->nr_to_scan)
break;
}
spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);