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From:   yanfei.xu@windriver.com
To:     linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] mm: khugepaged: check MMF_DISABLE_THP ahead of iterating over vmas
Date:   Sun,  4 Apr 2021 23:33:11 +0800
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From: Yanfei Xu <yanfei.xu@windriver.com>

We could check MMF_DISABLE_THP ahead of iterating over all of vma.
Otherwise if some mm_struct contain a large number of vma, there will
be amounts meaningless cpu cycles cost.

BTW, drop an unnecessary cond_resched(), because there is a another
cond_resched() followed it and no consumed invocation between them.

Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
---
 mm/khugepaged.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 2efe1d0c92ed..c293ec4a94ea 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2094,6 +2094,8 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
 	 */
 	if (unlikely(!mmap_read_trylock(mm)))
 		goto breakouterloop_mmap_lock;
+	if (test_bit(MMF_DISABLE_THP, &mm->flags))
+		goto breakouterloop_mmap_lock;
 	if (likely(!khugepaged_test_exit(mm)))
 		vma = find_vma(mm, khugepaged_scan.address);
 
@@ -2101,7 +2103,6 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
 	for (; vma; vma = vma->vm_next) {
 		unsigned long hstart, hend;
 
-		cond_resched();
 		if (unlikely(khugepaged_test_exit(mm))) {
 			progress++;
 			break;
-- 
2.27.0