linux-kernel - [PATCH v2 2/2] rcu/kvfree: Switch to expedited version in slow path

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Message-Id: <20240904143938.119964-3-urezki@gmail.com>
Date: Wed,  4 Sep 2024 16:39:38 +0200
From: "Uladzislau Rezki (Sony)" <urezki@...il.com>
To: "Paul E . McKenney" <paulmck@...nel.org>
Cc: RCU <rcu@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Neeraj upadhyay <Neeraj.Upadhyay@....com>,
	Boqun Feng <boqun.feng@...il.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Uladzislau Rezki <urezki@...il.com>,
	Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>
Subject: [PATCH v2 2/2] rcu/kvfree: Switch to expedited version in slow path

For a single argument and its slow path, switch to expedited
version of synchronize_rcu(). This version is considered to
be more faster, thus under a high memory pressure a slow path
becoms more efficient.

Note, latency-sensitive workloads should use rcutree.gp_normal=1,
which will make that synchronize_rcu_expedited() act like a regular
synchronize_rcu(), so no harm done to them.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 182772494cb0..87a64fcffa7f 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3856,7 +3856,7 @@ void kvfree_call_rcu(struct rcu_head *head, void *ptr)
 	 */
 	if (!success) {
 		debug_rcu_head_unqueue((struct rcu_head *) ptr);
-		cond_synchronize_rcu_full(&old_snap);
+		cond_synchronize_rcu_expedited_full(&old_snap);
 		kvfree(ptr);
 	}
 }
-- 
2.39.2