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refscale: Add a "jiffies" test 

This commit adds a "jiffies" test to refscale, allowing use of jiffies
to be compared to ktime_get_real_fast_ns().  On my x86 laptop, jiffies
is more than 20x faster.  (Though for many uses, the tens-of-nanoseconds
overhead of ktime_get_real_fast_ns() will be just fine.)

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2023-07-11 18:01:38 -07:00
parent f5063e8948
commit b5a2801fc0
1 changed files with 33 additions and 1 deletions
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34
kernel/rcu/refscale.c
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@ -528,6 +528,38 @@ static struct ref_scale_ops clock_ops = {
.name = "clock"
};
static void ref_jiffies_section(const int nloops)
{
u64 x = 0;
int i;
preempt_disable();
for (i = nloops; i >= 0; i--)
x += jiffies;
preempt_enable();
stopopts = x;
}
static void ref_jiffies_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 += jiffies;
un_delay(udl, ndl);
}
preempt_enable();
stopopts = x;
}
static struct ref_scale_ops jiffies_ops = {
.readsection = ref_jiffies_section,
.delaysection = ref_jiffies_delay_section,
.name = "jiffies"
};
////////////////////////////////////////////////////////////////////////
//
// Methods leveraging SLAB_TYPESAFE_BY_RCU.
@ -1047,7 +1079,7 @@ 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, &clock_ops,
&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops, &jiffies_ops,
&typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops,
};