[PATCH v7 05/10] mm/mlock: optimize munlock_pagevec by relocking

Alex Shi
2019-12-25T09:04:53Z

During the pagevec locking, a new page's lruvec is may same as
previous one. Thus we could save a re-locking, and only
change lock iff lruvec is newer.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: linux-kernel@vger.kernel.org
Cc: cgroups@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
---
mm/mlock.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/mm/mlock.c b/mm/mlock.c
index 10d15f58b061..050f999eadb1 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -289,6 +289,7 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
{
int i;
int nr = pagevec_count(pvec);
+ int delta_munlocked = -nr;
struct pagevec pvec_putback;
struct lruvec *lruvec = NULL;
int pgrescued = 0;
@@ -299,20 +300,19 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
for (i = 0; i < nr; i++) {
struct page *page = pvec->pages[i];

- lruvec = lock_page_lruvec_irq(page);
+ lruvec = relock_page_lruvec_irq(page, lruvec);

if (TestClearPageMlocked(page)) {
/*
* We already have pin from follow_page_mask()
* so we can spare the get_page() here.
*/
- if (__munlock_isolate_lru_page(page, lruvec, false)) {
- __mod_zone_page_state(zone, NR_MLOCK, -1);
- unlock_page_lruvec_irq(lruvec);
+ if (__munlock_isolate_lru_page(page, lruvec, false))
continue;
- } else
+ else
__munlock_isolation_failed(page);
- }
+ } else
+ delta_munlocked++;

/*
* We won't be munlocking this page in the next phase
@@ -322,8 +322,10 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
*/
pagevec_add(&pvec_putback, pvec->pages[i]);
pvec->pages[i] = NULL;
- unlock_page_lruvec_irq(lruvec);
}
+ __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
+ if (lruvec)
+ unlock_page_lruvec_irq(lruvec);

/* Now we can release pins of pages that we are not munlocking */
pagevec_release(&pvec_putback);
--
1.8.3.1