diff mbox series

[v18,25/32] mm/mlock: remove lru_lock on TestClearPageMlocked in munlock_vma_page

Message ID 1598273705-69124-26-git-send-email-alex.shi@linux.alibaba.com (mailing list archive)
State New, archived
Headers show
Series per memcg lru_lock | expand

Commit Message

Alex Shi Aug. 24, 2020, 12:54 p.m. UTC 
In the func munlock_vma_page, the page must be PageLocked as well as
pages in split_huge_page series funcs. Thus the PageLocked is enough
to serialize both funcs.

So we could relief the TestClearPageMlocked/hpage_nr_pages which are not
necessary under lru lock.

As to another munlock func __munlock_pagevec, which no PageLocked
protection and should remain lru protecting.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/mlock.c | 41 +++++++++++++++--------------------------
 1 file changed, 15 insertions(+), 26 deletions(-)

Comments

Alex Shi Aug. 26, 2020, 5:52 a.m. UTC | #1 
LKP reported a preemptiable issue on this patch. update and refresh
the commit log.

From f18e8c87a045bbb8040006b6816ded1f55fa6f9c Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@linux.alibaba.com>
Date: Sat, 25 Jul 2020 22:31:03 +0800
Subject: [PATCH] mm/mlock: remove lru_lock on TestClearPageMlocked in
 munlock_vma_page

In the func munlock_vma_page, comments mentained lru_lock needed for
serialization with split_huge_pages. But the page must be PageLocked
as well as pages in split_huge_page series funcs. Thus the PageLocked
is enough to serialize both funcs.

So we could relief the TestClearPageMlocked/hpage_nr_pages which are not
necessary under lru lock.

As to another munlock func __munlock_pagevec, which no PageLocked
protection and should remain lru protecting.

LKP found a preempt issue on __mod_zone_page_state which need change
to mod_zone_page_state. Thanks!

Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/mlock.c | 43 ++++++++++++++++---------------------------
 1 file changed, 16 insertions(+), 27 deletions(-)

diff --git a/mm/mlock.c b/mm/mlock.c
index 0448409184e3..cd88b93b0f0d 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -69,9 +69,9 @@ void clear_page_mlock(struct page *page)
 	 *
 	 * See __pagevec_lru_add_fn for more explanation.
 	 */
-	if (!isolate_lru_page(page)) {
+	if (!isolate_lru_page(page))
 		putback_lru_page(page);
-	} else {
+	else {
 		/*
 		 * We lost the race. the page already moved to evictable list.
 		 */
@@ -178,7 +178,6 @@ static void __munlock_isolation_failed(struct page *page)
 unsigned int munlock_vma_page(struct page *page)
 {
 	int nr_pages;
-	struct lruvec *lruvec;
 
 	/* For try_to_munlock() and to serialize with page migration */
 	BUG_ON(!PageLocked(page));
@@ -186,37 +185,22 @@ unsigned int munlock_vma_page(struct page *page)
 	VM_BUG_ON_PAGE(PageTail(page), page);
 
 	/*
-	 * Serialize split tail pages in __split_huge_page_tail() which
-	 * might otherwise copy PageMlocked to part of the tail pages before
-	 * we clear it in the head page. It also stabilizes thp_nr_pages().
-	 * TestClearPageLRU can't be used here to block page isolation, since
-	 * out of lock clear_page_mlock may interfer PageLRU/PageMlocked
-	 * sequence, same as __pagevec_lru_add_fn, and lead the page place to
-	 * wrong lru list here. So relay on PageLocked to stop lruvec change
-	 * in mem_cgroup_move_account().
+	 * Serialize split tail pages in __split_huge_page_tail() by
+	 * lock_page(); Do TestClearPageMlocked/PageLRU sequence like
+	 * clear_page_mlock().
 	 */
-	lruvec = lock_page_lruvec_irq(page);
-
-	if (!TestClearPageMlocked(page)) {
+	if (!TestClearPageMlocked(page))
 		/* Potentially, PTE-mapped THP: do not skip the rest PTEs */
-		nr_pages = 1;
-		goto unlock_out;
-	}
+		return 0;
 
 	nr_pages = thp_nr_pages(page);
-	__mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
+	mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
 
-	if (__munlock_isolate_lru_page(page, lruvec, true)) {
-		unlock_page_lruvec_irq(lruvec);
+	if (!isolate_lru_page(page))
 		__munlock_isolated_page(page);
-		goto out;
-	}
-	__munlock_isolation_failed(page);
-
-unlock_out:
-	unlock_page_lruvec_irq(lruvec);
+	else
+		__munlock_isolation_failed(page);
 
-out:
 	return nr_pages - 1;
 }
 
@@ -305,6 +289,11 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
 
 		/* block memcg change in mem_cgroup_move_account */
 		lock_page_memcg(page);
+		/*
+		 * Serialize split tail pages in __split_huge_page_tail() which
+		 * might otherwise copy PageMlocked to part of the tail pages
+		 * before we clear it in the head page.
+		 */
 		lruvec = relock_page_lruvec_irq(page, lruvec);
 		if (TestClearPageMlocked(page)) {
 			/*
Hugh Dickins Sept. 22, 2020, 6:13 a.m. UTC | #2 
On Mon, 24 Aug 2020, Alex Shi wrote:

> In the func munlock_vma_page, the page must be PageLocked as well as
> pages in split_huge_page series funcs. Thus the PageLocked is enough
> to serialize both funcs.
> 
> So we could relief the TestClearPageMlocked/hpage_nr_pages which are not
> necessary under lru lock.
> 
> As to another munlock func __munlock_pagevec, which no PageLocked
> protection and should remain lru protecting.
> 
> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>

I made some comments on the mlock+munlock situation last week:
I won't review this 24/32 and 25/32 now, but will take a look
at your github tree tomorrow instead.  Perhaps I'll find you have
already done the fixes, perhaps I'll find you have merged these back
into earlier patches.  And I won't be reviewing beyond this point:
this is enough for now, I think.

Hugh

> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  mm/mlock.c | 41 +++++++++++++++--------------------------
>  1 file changed, 15 insertions(+), 26 deletions(-)
> 
> diff --git a/mm/mlock.c b/mm/mlock.c
> index 0448409184e3..46a05e6ec5ba 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -69,9 +69,9 @@ void clear_page_mlock(struct page *page)
>  	 *
>  	 * See __pagevec_lru_add_fn for more explanation.
>  	 */
> -	if (!isolate_lru_page(page)) {
> +	if (!isolate_lru_page(page))
>  		putback_lru_page(page);
> -	} else {
> +	else {
>  		/*
>  		 * We lost the race. the page already moved to evictable list.
>  		 */
> @@ -178,7 +178,6 @@ static void __munlock_isolation_failed(struct page *page)
>  unsigned int munlock_vma_page(struct page *page)
>  {
>  	int nr_pages;
> -	struct lruvec *lruvec;
>  
>  	/* For try_to_munlock() and to serialize with page migration */
>  	BUG_ON(!PageLocked(page));
> @@ -186,37 +185,22 @@ unsigned int munlock_vma_page(struct page *page)
>  	VM_BUG_ON_PAGE(PageTail(page), page);
>  
>  	/*
> -	 * Serialize split tail pages in __split_huge_page_tail() which
> -	 * might otherwise copy PageMlocked to part of the tail pages before
> -	 * we clear it in the head page. It also stabilizes thp_nr_pages().
> -	 * TestClearPageLRU can't be used here to block page isolation, since
> -	 * out of lock clear_page_mlock may interfer PageLRU/PageMlocked
> -	 * sequence, same as __pagevec_lru_add_fn, and lead the page place to
> -	 * wrong lru list here. So relay on PageLocked to stop lruvec change
> -	 * in mem_cgroup_move_account().
> +	 * Serialize split tail pages in __split_huge_page_tail() by
> +	 * lock_page(); Do TestClearPageMlocked/PageLRU sequence like
> +	 * clear_page_mlock().
>  	 */
> -	lruvec = lock_page_lruvec_irq(page);
> -
> -	if (!TestClearPageMlocked(page)) {
> +	if (!TestClearPageMlocked(page))
>  		/* Potentially, PTE-mapped THP: do not skip the rest PTEs */
> -		nr_pages = 1;
> -		goto unlock_out;
> -	}
> +		return 0;
>  
>  	nr_pages = thp_nr_pages(page);
>  	__mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
>  
> -	if (__munlock_isolate_lru_page(page, lruvec, true)) {
> -		unlock_page_lruvec_irq(lruvec);
> +	if (!isolate_lru_page(page))
>  		__munlock_isolated_page(page);
> -		goto out;
> -	}
> -	__munlock_isolation_failed(page);
> -
> -unlock_out:
> -	unlock_page_lruvec_irq(lruvec);
> +	else
> +		__munlock_isolation_failed(page);
>  
> -out:
>  	return nr_pages - 1;
>  }
>  
> @@ -305,6 +289,11 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
>  
>  		/* block memcg change in mem_cgroup_move_account */
>  		lock_page_memcg(page);
> +		/*
> +		 * Serialize split tail pages in __split_huge_page_tail() which
> +		 * might otherwise copy PageMlocked to part of the tail pages
> +		 * before we clear it in the head page.
> +		 */
>  		lruvec = relock_page_lruvec_irq(page, lruvec);
>  		if (TestClearPageMlocked(page)) {
>  			/*
> -- 
> 1.8.3.1
> 
>
Alex Shi Sept. 23, 2020, 1:58 a.m. UTC | #3 
在 2020/9/22 下午2:13, Hugh Dickins 写道:
> On Mon, 24 Aug 2020, Alex Shi wrote:
> 
>> In the func munlock_vma_page, the page must be PageLocked as well as
>> pages in split_huge_page series funcs. Thus the PageLocked is enough
>> to serialize both funcs.
>>
>> So we could relief the TestClearPageMlocked/hpage_nr_pages which are not
>> necessary under lru lock.
>>
>> As to another munlock func __munlock_pagevec, which no PageLocked
>> protection and should remain lru protecting.
>>
>> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
> I made some comments on the mlock+munlock situation last week:
> I won't review this 24/32 and 25/32 now, but will take a look
> at your github tree tomorrow instead.  Perhaps I'll find you have
> already done the fixes, perhaps I'll find you have merged these back
> into earlier patches.  And I won't be reviewing beyond this point:
> this is enough for now, I think.
> 

Yes, these 2 patches was fixed as your suggested on 
https://github.com/alexshi/linux.git lruv19.5 

83f8582dcd5a mm/mlock: remove lru_lock on TestClearPageMlocked
20836d10f0ed mm/mlock: remove __munlock_isolate_lru_page

Thanks!
Alex
diff mbox series

Patch

diff --git a/mm/mlock.c b/mm/mlock.c
index 0448409184e3..46a05e6ec5ba 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -69,9 +69,9 @@  void clear_page_mlock(struct page *page)
 	 *
 	 * See __pagevec_lru_add_fn for more explanation.
 	 */
-	if (!isolate_lru_page(page)) {
+	if (!isolate_lru_page(page))
 		putback_lru_page(page);
-	} else {
+	else {
 		/*
 		 * We lost the race. the page already moved to evictable list.
 		 */
@@ -178,7 +178,6 @@  static void __munlock_isolation_failed(struct page *page)
 unsigned int munlock_vma_page(struct page *page)
 {
 	int nr_pages;
-	struct lruvec *lruvec;
 
 	/* For try_to_munlock() and to serialize with page migration */
 	BUG_ON(!PageLocked(page));
@@ -186,37 +185,22 @@  unsigned int munlock_vma_page(struct page *page)
 	VM_BUG_ON_PAGE(PageTail(page), page);
 
 	/*
-	 * Serialize split tail pages in __split_huge_page_tail() which
-	 * might otherwise copy PageMlocked to part of the tail pages before
-	 * we clear it in the head page. It also stabilizes thp_nr_pages().
-	 * TestClearPageLRU can't be used here to block page isolation, since
-	 * out of lock clear_page_mlock may interfer PageLRU/PageMlocked
-	 * sequence, same as __pagevec_lru_add_fn, and lead the page place to
-	 * wrong lru list here. So relay on PageLocked to stop lruvec change
-	 * in mem_cgroup_move_account().
+	 * Serialize split tail pages in __split_huge_page_tail() by
+	 * lock_page(); Do TestClearPageMlocked/PageLRU sequence like
+	 * clear_page_mlock().
 	 */
-	lruvec = lock_page_lruvec_irq(page);
-
-	if (!TestClearPageMlocked(page)) {
+	if (!TestClearPageMlocked(page))
 		/* Potentially, PTE-mapped THP: do not skip the rest PTEs */
-		nr_pages = 1;
-		goto unlock_out;
-	}
+		return 0;
 
 	nr_pages = thp_nr_pages(page);
 	__mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
 
-	if (__munlock_isolate_lru_page(page, lruvec, true)) {
-		unlock_page_lruvec_irq(lruvec);
+	if (!isolate_lru_page(page))
 		__munlock_isolated_page(page);
-		goto out;
-	}
-	__munlock_isolation_failed(page);
-
-unlock_out:
-	unlock_page_lruvec_irq(lruvec);
+	else
+		__munlock_isolation_failed(page);
 
-out:
 	return nr_pages - 1;
 }
 
@@ -305,6 +289,11 @@  static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
 
 		/* block memcg change in mem_cgroup_move_account */
 		lock_page_memcg(page);
+		/*
+		 * Serialize split tail pages in __split_huge_page_tail() which
+		 * might otherwise copy PageMlocked to part of the tail pages
+		 * before we clear it in the head page.
+		 */
 		lruvec = relock_page_lruvec_irq(page, lruvec);
 		if (TestClearPageMlocked(page)) {
 			/*