linux-kernel - [PATCH rcu 1/7] refscale: Add measurement of clock readout

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210721210441.796995-1-paulmck@kernel.org>
Date:   Wed, 21 Jul 2021 14:04:35 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, akpm@...ux-foundation.org,
        mathieu.desnoyers@...icios.com, josh@...htriplett.org,
        tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 1/7] refscale: Add measurement of clock readout

This commit adds a "clock" type to refscale, which checks the performance
of ktime_get_real_fast_ns().  Use the "clocksource=" kernel boot parameter
to select the underlying clock source.

[ paulmck: Work around compiler false positive per kernel test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/refscale.c | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index d998a76fb5422..cba737cb246e8 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -467,6 +467,41 @@ static struct ref_scale_ops acqrel_ops = {
 	.name		= "acqrel"
 };
 
+static volatile u64 stopopts;
+
+static void ref_clock_section(const int nloops)
+{
+	u64 x = 0;
+	int i;
+
+	preempt_disable();
+	for (i = nloops; i >= 0; i--) {
+		x += ktime_get_real_fast_ns();
+	}
+	preempt_enable();
+	stopopts = x;
+}
+
+static void ref_clock_delay_section(const int nloops, const int udl, const int ndl)
+{
+	u64 x = 0;
+	int i;
+
+	preempt_disable();
+	for (i = nloops; i >= 0; i--) {
+		x += ktime_get_real_fast_ns();
+		un_delay(udl, ndl);
+	}
+	preempt_enable();
+	stopopts = x;
+}
+
+static struct ref_scale_ops clock_ops = {
+	.readsection	= ref_clock_section,
+	.delaysection	= ref_clock_delay_section,
+	.name		= "clock"
+};
+
 static void rcu_scale_one_reader(void)
 {
 	if (readdelay <= 0)
@@ -759,7 +794,7 @@ ref_scale_init(void)
 	int firsterr = 0;
 	static struct ref_scale_ops *scale_ops[] = {
 		&rcu_ops, &srcu_ops, &rcu_trace_ops, &rcu_tasks_ops, &refcnt_ops, &rwlock_ops,
-		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops,
+		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops,
 	};
 
 	if (!torture_init_begin(scale_type, verbose))
-- 
2.31.1.189.g2e36527f23