[RFC PATCH 1/3] mm, thp: revert allocstall comparing

From: Ebru Akagunduz
Date: Sat Jun 11 2016 - 15:16:23 EST


This patch takes back allocstall comparing when deciding
whether swapin worthwhile because it does not work,
if vmevent disabled.

Related commit:
http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=2548306628308aa6a326640d345a737bc898941d

Signed-off-by: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx>
---
mm/khugepaged.c | 31 ++++++++-----------------------
1 file changed, 8 insertions(+), 23 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 0ac63f7..e3d8da7 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -68,7 +68,6 @@ static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
*/
static unsigned int khugepaged_max_ptes_none __read_mostly;
static unsigned int khugepaged_max_ptes_swap __read_mostly;
-static unsigned long allocstall;

static int khugepaged(void *none);

@@ -926,7 +925,6 @@ static void collapse_huge_page(struct mm_struct *mm,
struct page *new_page;
spinlock_t *pmd_ptl, *pte_ptl;
int isolated = 0, result = 0;
- unsigned long swap, curr_allocstall;
struct mem_cgroup *memcg;
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
@@ -955,8 +953,6 @@ static void collapse_huge_page(struct mm_struct *mm,
goto out_nolock;
}

- swap = get_mm_counter(mm, MM_SWAPENTS);
- curr_allocstall = sum_vm_event(ALLOCSTALL);
down_read(&mm->mmap_sem);
result = hugepage_vma_revalidate(mm, address);
if (result) {
@@ -972,22 +968,15 @@ static void collapse_huge_page(struct mm_struct *mm,
up_read(&mm->mmap_sem);
goto out_nolock;
}
-
/*
- * Don't perform swapin readahead when the system is under pressure,
- * to avoid unnecessary resource consumption.
+ * __collapse_huge_page_swapin always returns with mmap_sem
+ * locked. If it fails, release mmap_sem and jump directly
+ * out. Continuing to collapse causes inconsistency.
*/
- if (allocstall == curr_allocstall && swap != 0) {
- /*
- * __collapse_huge_page_swapin always returns with mmap_sem
- * locked. If it fails, release mmap_sem and jump directly
- * out. Continuing to collapse causes inconsistency.
- */
- if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) {
- mem_cgroup_cancel_charge(new_page, memcg, true);
- up_read(&mm->mmap_sem);
- goto out_nolock;
- }
+ if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) {
+ mem_cgroup_cancel_charge(new_page, memcg, true);
+ up_read(&mm->mmap_sem);
+ goto out_nolock;
}

up_read(&mm->mmap_sem);
@@ -1822,7 +1811,6 @@ static void khugepaged_wait_work(void)
if (!scan_sleep_jiffies)
return;

- allocstall = sum_vm_event(ALLOCSTALL);
khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
wait_event_freezable_timeout(khugepaged_wait,
khugepaged_should_wakeup(),
@@ -1830,10 +1818,8 @@ static void khugepaged_wait_work(void)
return;
}

- if (khugepaged_enabled()) {
- allocstall = sum_vm_event(ALLOCSTALL);
+ if (khugepaged_enabled())
wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
- }
}

static int khugepaged(void *none)
@@ -1842,7 +1828,6 @@ static int khugepaged(void *none)

set_freezable();
set_user_nice(current, MAX_NICE);
- allocstall = sum_vm_event(ALLOCSTALL);

while (!kthread_should_stop()) {
khugepaged_do_scan();
--
1.9.1