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From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     rcu@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, kernel-team@meta.com,
        rostedt@goodmis.org, hch@lst.de,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Sachin Sant <sachinp@linux.ibm.com>,
        "Zhang, Qiang1" <qiang1.zhang@intel.com>
Subject: [PATCH rcu 13/20] srcu: Move ->sda_is_static from srcu_struct to srcu_usage
Date:   Thu, 30 Mar 2023 15:47:19 -0700
Message-Id: <20230330224726.662344-13-paulmck@kernel.org>
In-Reply-To: <f1b6cd5f-f0b7-4748-abd5-0dcfef0ce126@paulmck-laptop>
References: <f1b6cd5f-f0b7-4748-abd5-0dcfef0ce126@paulmck-laptop>
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Precedence: bulk

This commit moves the ->sda_is_static field from the srcu_struct structure
to the srcu_usage structure to reduce the size of the former in order
to improve cache locality.

Suggested-by: Christoph Hellwig <hch@lst.de>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Tested-by: "Zhang, Qiang1" <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 include/linux/srcutree.h | 2 +-
 kernel/rcu/srcutree.c    | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 3023492d8d89..d3534ecb806e 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -76,6 +76,7 @@ struct srcu_usage {
 	unsigned long srcu_size_jiffies;	/* Current contention-measurement interval. */
 	unsigned long srcu_n_lock_retries;	/* Contention events in current interval. */
 	unsigned long srcu_n_exp_nodelay;	/* # expedited no-delays in current GP phase. */
+	bool sda_is_static;			/* May ->sda be passed to free_percpu()? */
 };
 
 /*
@@ -84,7 +85,6 @@ struct srcu_usage {
 struct srcu_struct {
 	unsigned int srcu_idx;			/* Current rdr array element. */
 	struct srcu_data __percpu *sda;		/* Per-CPU srcu_data array. */
-	bool sda_is_static;			/* May ->sda be passed to free_percpu()? */
 	unsigned long srcu_barrier_seq;		/* srcu_barrier seq #. */
 	struct mutex srcu_barrier_mutex;	/* Serialize barrier ops. */
 	struct completion srcu_barrier_completion;
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 291fb520bce0..20f2373f7e25 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -252,7 +252,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
 	mutex_init(&ssp->srcu_barrier_mutex);
 	atomic_set(&ssp->srcu_barrier_cpu_cnt, 0);
 	INIT_DELAYED_WORK(&ssp->work, process_srcu);
-	ssp->sda_is_static = is_static;
+	ssp->srcu_sup->sda_is_static = is_static;
 	if (!is_static)
 		ssp->sda = alloc_percpu(struct srcu_data);
 	if (!ssp->sda) {
@@ -265,7 +265,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
 	ssp->srcu_sup->srcu_last_gp_end = ktime_get_mono_fast_ns();
 	if (READ_ONCE(ssp->srcu_sup->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) {
 		if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC)) {
-			if (!ssp->sda_is_static) {
+			if (!ssp->srcu_sup->sda_is_static) {
 				free_percpu(ssp->sda);
 				ssp->sda = NULL;
 				kfree(ssp->srcu_sup);
@@ -667,7 +667,7 @@ void cleanup_srcu_struct(struct srcu_struct *ssp)
 	kfree(ssp->srcu_sup->node);
 	ssp->srcu_sup->node = NULL;
 	ssp->srcu_sup->srcu_size_state = SRCU_SIZE_SMALL;
-	if (!ssp->sda_is_static) {
+	if (!ssp->srcu_sup->sda_is_static) {
 		free_percpu(ssp->sda);
 		ssp->sda = NULL;
 		kfree(ssp->srcu_sup);
@@ -1906,7 +1906,7 @@ static void srcu_module_going(struct module *mod)
 	for (i = 0; i < mod->num_srcu_structs; i++) {
 		ssp = *(sspp++);
 		if (!rcu_seq_state(smp_load_acquire(&ssp->srcu_sup->srcu_gp_seq_needed)) &&
-		    !WARN_ON_ONCE(!ssp->sda_is_static))
+		    !WARN_ON_ONCE(!ssp->srcu_sup->sda_is_static))
 			cleanup_srcu_struct(ssp);
 		free_percpu(ssp->sda);
 	}
-- 
2.40.0.rc2