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SubjectRe: [PATCH] thp: reduce khugepaged freezing latency
On Wed, Nov 09, 2011 at 10:34:47AM -0800, Tejun Heo wrote:
> know. My instinct tells me to strongly recommend use of
> wait_event_freezable_timeout() and run away. :)

Passing false wasn't so appealing to me but ok. Jiri can you test this
with some suspend? (beware builds but untested)

===
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>
---
mm/huge_memory.c | 14 ++++----------
1 files changed, 4 insertions(+), 10 deletions(-)

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());

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