From: Andrea Arcangeli <aarcange@redhat.com>

Subject: thp: reduce khugepaged freezing latency

Use wait_event_freezable_timeout() instead of

schedule_timeout_interruptible() to avoid missing freezer wakeups. A

try_to_freeze() would have been needed in the

khugepaged_alloc_hugepage tight loop too in case of the allocation

failing repeatedly, and wait_event_freezable_timeout will provide it

too.

khugepaged would still freeze just fine by trying again the next

minute but it's better if it freezes immediately.

Reported-by: Jiri Slaby <jslaby@suse.cz>

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c

index 4298aba..fd925d0 100644

--- a/mm/huge_memory.c

+++ b/mm/huge_memory.c

@@ -2259,12 +2259,9 @@ static void khugepaged_do_scan(struct page **hpage)

 static void khugepaged_alloc_sleep(void)

 {

-	DEFINE_WAIT(wait);

-	add_wait_queue(&khugepaged_wait, &wait);

-	schedule_timeout_interruptible(

-		msecs_to_jiffies(

-			khugepaged_alloc_sleep_millisecs));

-	remove_wait_queue(&khugepaged_wait, &wait);

+	wait_event_freezable_timeout(khugepaged_wait, false,

+				     msecs_to_jiffies(

+					     khugepaged_alloc_sleep_millisecs));

 }

 #ifndef CONFIG_NUMA

@@ -2313,14 +2310,11 @@ static void khugepaged_loop(void)

 		if (unlikely(kthread_should_stop()))

 			break;

 		if (khugepaged_has_work()) {

-			DEFINE_WAIT(wait);

 			if (!khugepaged_scan_sleep_millisecs)

 				continue;

-			add_wait_queue(&khugepaged_wait, &wait);

-			schedule_timeout_interruptible(

+			wait_event_freezable_timeout(khugepaged_wait, false,

 				msecs_to_jiffies(

 					khugepaged_scan_sleep_millisecs));

-			remove_wait_queue(&khugepaged_wait, &wait);

 		} else if (khugepaged_enabled())

 			wait_event_freezable(khugepaged_wait,

 					     khugepaged_wait_event());