[PATCH] memcg: Optimise relock_page_lruvec functions

Subsystems: control group - memory resource controller (memcg), the rest

STALE1744d

3 messages, 3 authors, 2021-10-25 · open the first message on its own page

[PATCH] memcg: Optimise relock_page_lruvec functions

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: 2021-10-19 12:53:46

Leave interrupts disabled when we change which lru lock is held.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/memcontrol.h | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 3096c9a0ee01..a6a90b00a22b 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h

@@ -1524,16 +1524,22 @@ static inline bool page_matches_lruvec(struct page *page, struct lruvec *lruvec)
 }
 
 /* Don't lock again iff page's lruvec locked */
-static inline struct lruvec *relock_page_lruvec_irq(struct page *page,
+static inline struct lruvec *relock_page_lruvec(struct page *page,
 		struct lruvec *locked_lruvec)
 {
-	if (locked_lruvec) {
-		if (page_matches_lruvec(page, locked_lruvec))
-			return locked_lruvec;
+	if (page_matches_lruvec(page, locked_lruvec))
+		return locked_lruvec;
 
-		unlock_page_lruvec_irq(locked_lruvec);
-	}
+	unlock_page_lruvec(locked_lruvec);
+	return lock_page_lruvec(page);
+}
 
+/* Don't lock again iff page's lruvec locked */
+static inline struct lruvec *relock_page_lruvec_irq(struct page *page,
+		struct lruvec *locked_lruvec)
+{
+	if (locked_lruvec)
+		return relock_page_lruvec(page, locked_lruvec);
 	return lock_page_lruvec_irq(page);
 }

@@ -1541,13 +1547,8 @@ static inline struct lruvec *relock_page_lruvec_irq(struct page *page,
 static inline struct lruvec *relock_page_lruvec_irqsave(struct page *page,
 		struct lruvec *locked_lruvec, unsigned long *flags)
 {
-	if (locked_lruvec) {
-		if (page_matches_lruvec(page, locked_lruvec))
-			return locked_lruvec;
-
-		unlock_page_lruvec_irqrestore(locked_lruvec, *flags);
-	}
-
+	if (locked_lruvec)
+		return relock_page_lruvec(page, locked_lruvec);
 	return lock_page_lruvec_irqsave(page, flags);
 }

-- 
2.32.0

Re: [PATCH] memcg: Optimise relock_page_lruvec functions

From: Vlastimil Babka <hidden>
Date: 2021-10-25 10:44:09

On 10/19/21 14:50, Matthew Wilcox (Oracle) wrote:

Leave interrupts disabled when we change which lru lock is held.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Acked-by: Vlastimil Babka <redacted>

Assuming lockdep is fine with e.g.:

spin_lock_irqsave(A);
spin_unlock(A);
spin_lock(B);
spin_unlock_irqrestore(B);

(with A and B of same class).

quoted hunk

---
 include/linux/memcontrol.h | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 3096c9a0ee01..a6a90b00a22b 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h

@@ -1524,16 +1524,22 @@ static inline bool page_matches_lruvec(struct page *page, struct lruvec *lruvec)
 }
 
 /* Don't lock again iff page's lruvec locked */
-static inline struct lruvec *relock_page_lruvec_irq(struct page *page,
+static inline struct lruvec *relock_page_lruvec(struct page *page,
 		struct lruvec *locked_lruvec)
 {
-	if (locked_lruvec) {
-		if (page_matches_lruvec(page, locked_lruvec))
-			return locked_lruvec;
+	if (page_matches_lruvec(page, locked_lruvec))
+		return locked_lruvec;
 
-		unlock_page_lruvec_irq(locked_lruvec);
-	}
+	unlock_page_lruvec(locked_lruvec);
+	return lock_page_lruvec(page);
+}
 
+/* Don't lock again iff page's lruvec locked */
+static inline struct lruvec *relock_page_lruvec_irq(struct page *page,
+		struct lruvec *locked_lruvec)
+{
+	if (locked_lruvec)
+		return relock_page_lruvec(page, locked_lruvec);
 	return lock_page_lruvec_irq(page);
 }

@@ -1541,13 +1547,8 @@ static inline struct lruvec *relock_page_lruvec_irq(struct page *page,
 static inline struct lruvec *relock_page_lruvec_irqsave(struct page *page,
 		struct lruvec *locked_lruvec, unsigned long *flags)
 {
-	if (locked_lruvec) {
-		if (page_matches_lruvec(page, locked_lruvec))
-			return locked_lruvec;
-
-		unlock_page_lruvec_irqrestore(locked_lruvec, *flags);
-	}
-
+	if (locked_lruvec)
+		return relock_page_lruvec(page, locked_lruvec);
 	return lock_page_lruvec_irqsave(page, flags);
 }

Re: [PATCH] memcg: Optimise relock_page_lruvec functions

From: Peter Zijlstra <peterz@infradead.org>
Date: 2021-10-25 11:16:55

On Mon, Oct 25, 2021 at 12:44:05PM +0200, Vlastimil Babka wrote:

On 10/19/21 14:50, Matthew Wilcox (Oracle) wrote:

quoted

Leave interrupts disabled when we change which lru lock is held.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Acked-by: Vlastimil Babka <redacted>

Assuming lockdep is fine with e.g.:

spin_lock_irqsave(A);
spin_unlock(A);
spin_lock(B);
spin_unlock_irqrestore(B);

(with A and B of same class).

It's unconditionally okay with that pattern. As far as lockdep
is concerned there really is no differences vs:

	local_irq_save()
	spin_lock(a)
	spin_unlock(a)
	spin_lock(b)
	spin_unlock(b)
	local_irq_restore()

It's the RT locking primitives that care about the difference :-)

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