linux-kernel - [PATCH 1/1] rcu/kvfree: Do not run a page work if a cache is disabled

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Message-Id: <20230411131341.9910-1-urezki@gmail.com>
Date:   Tue, 11 Apr 2023 15:13:41 +0200
From:   "Uladzislau Rezki (Sony)" <urezki@...il.com>
To:     "Paul E . McKenney" <paulmck@...nel.org>
Cc:     RCU <rcu@...r.kernel.org>, quic_neeraju@...cinc.com,
        Boqun Feng <boqun.feng@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: [PATCH 1/1] rcu/kvfree: Do not run a page work if a cache is disabled

By default the cache size is 5 pages per-cpu. But it can
be disabled at boot time by setting the rcu_min_cached_objs
to zero.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 kernel/rcu/tree.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 35be35f8236b..21e3d9dffde5 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3246,6 +3246,10 @@ static void fill_page_cache_func(struct work_struct *work)
 static void
 run_page_cache_worker(struct kfree_rcu_cpu *krcp)
 {
+	// If cache disabled, bail out.
+	if (!rcu_min_cached_objs)
+		return;
+
 	if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
 			!atomic_xchg(&krcp->work_in_progress, 1)) {
 		if (atomic_read(&krcp->backoff_page_cache_fill)) {
-- 
2.30.2