From 25f6fa53a07422e2bb004229eefd32760c469fb0 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 3 May 2021 17:04:57 -0700 Subject: [PATCH] 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 --- kernel/rcu/refscale.c | 36 +++++++++++++++++++++++++++++++++++- 1 file changed, 35 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c index d998a76fb542..66dc14cf5687 100644 --- a/kernel/rcu/refscale.c +++ b/kernel/rcu/refscale.c @@ -467,6 +467,40 @@ 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 +793,7 @@ 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))