+ mm-lru_cache_disable-use-synchronize_rcu_expedited.patch added to mm-hotfixes-unstable branch

+ mm-lru_cache_disable-use-synchronize_rcu_expedited.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm: lru_cache_disable: use synchronize_rcu_expedited
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-lru_cache_disable-use-synchronize_rcu_expedited.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-lru_cache_disable-use-synchronize_rcu_expedited.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: mm: lru_cache_disable: use synchronize_rcu_expedited
Date: Mon, 30 May 2022 12:51:56 -0300

commit ff042f4a9b050 ("mm: lru_cache_disable: replace work queue
synchronization with synchronize_rcu") replaced lru_cache_disable's usage
of work queues with synchronize_rcu.

Some users reported large performance regressions due to this commit, for
example:
https://lore.kernel.org/all/20220521234616.GO1790663@paulmck-ThinkPad-P17-Gen-1/T/

Switching to synchronize_rcu_expedited fixes the problem.

Link: https://lkml.kernel.org/r/YpToHCmnx/HEcVyR@fuller.cnet
Fixes: ff042f4a9b050 ("mm: lru_cache_disable: replace work queue synchronization with synchronize_rcu")
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Tested-by: Michael Larabel <Michael@MichaelLarabel.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Phil Elwell <phil@raspberrypi.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/swap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/swap.c~mm-lru_cache_disable-use-synchronize_rcu_expedited
+++ a/mm/swap.c
@@ -881,7 +881,7 @@ void lru_cache_disable(void)
 	 * lru_disable_count = 0 will have exited the critical
 	 * section when synchronize_rcu() returns.
 	 */
-	synchronize_rcu();
+	synchronize_rcu_expedited();
 #ifdef CONFIG_SMP
 	__lru_add_drain_all(true);
 #else
_

Patches currently in -mm which might be from mtosatti@redhat.com are

mm-lru_cache_disable-use-synchronize_rcu_expedited.patch