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refscale: Add measurement of clock readout

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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@kernel.org>
This commit is contained in:
Paul E. McKenney 2021-05-03 17:04:57 -07:00
parent 2734d6c1b1
commit 25f6fa53a0
1 changed files with 35 additions and 1 deletions
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36
kernel/rcu/refscale.c
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@ -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))