thp: reduce khugepaged freezing latency

khugepaged can sometimes cause suspend to fail, requiring that the user
retry the suspend operation.

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>
Tested-by: Jiri Slaby <jslaby@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: "Rafael J. Wysocki" <rjw@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4298aba..36b3d98 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2259,12 +2259,8 @@ 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 +2309,10 @@ 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(
-                               msecs_to_jiffies(
-                                       khugepaged_scan_sleep_millisecs));
-                       remove_wait_queue(&khugepaged_wait, &wait);
+                       wait_event_freezable_timeout(khugepaged_wait, false,
+                           msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
                } else if (khugepaged_enabled())
                        wait_event_freezable(khugepaged_wait,
                                             khugepaged_wait_event());