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rcuscale: Add laziness and kfree tests

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This commit adds 2 tests to rcuscale.  The first one is a startup test
to check whether we are not too lazy or too hard working.  The second
one causes kfree_rcu() itself to use call_rcu() and checks memory
pressure. Testing indicates that the new call_rcu() keeps memory pressure
under control roughly as well as does kfree_rcu().

[ paulmck: Apply checkpatch feedback. ]

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Joel Fernandes (Google) 2022-10-16 16:22:57 +00:00 committed by Paul E. McKenney
parent c945b4da7a
commit 084e04fff1
1 changed files with 65 additions and 2 deletions
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67
kernel/rcu/rcuscale.c
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@ -95,6 +95,7 @@ torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() scale test?");
torture_param(int, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");
torture_param(int, kfree_by_call_rcu, 0, "Use call_rcu() to emulate kfree_rcu()?");
static char *scale_type = "rcu";
module_param(scale_type, charp, 0444);
@ -659,6 +660,14 @@ struct kfree_obj {
struct rcu_head rh;
};
/* Used if doing RCU-kfree'ing via call_rcu(). */
static void kfree_call_rcu(struct rcu_head *rh)
{
struct kfree_obj *obj = container_of(rh, struct kfree_obj, rh);
kfree(obj);
}
static int
kfree_scale_thread(void *arg)
{
@ -696,6 +705,11 @@ kfree_scale_thread(void *arg)
if (!alloc_ptr)
return -ENOMEM;
if (kfree_by_call_rcu) {
call_rcu(&(alloc_ptr->rh), kfree_call_rcu);
continue;
}
// By default kfree_rcu_test_single and kfree_rcu_test_double are
// initialized to false. If both have the same value (false or true)
// both are randomly tested, otherwise only the one with value true
@ -767,11 +781,58 @@ kfree_scale_shutdown(void *arg)
return -EINVAL;
}
// Used if doing RCU-kfree'ing via call_rcu().
static unsigned long jiffies_at_lazy_cb;
static struct rcu_head lazy_test1_rh;
static int rcu_lazy_test1_cb_called;
static void call_rcu_lazy_test1(struct rcu_head *rh)
{
jiffies_at_lazy_cb = jiffies;
WRITE_ONCE(rcu_lazy_test1_cb_called, 1);
}
static int __init
kfree_scale_init(void)
{
long i;
int firsterr = 0;
long i;
unsigned long jif_start;
unsigned long orig_jif;
// Also, do a quick self-test to ensure laziness is as much as
// expected.
if (kfree_by_call_rcu && !IS_ENABLED(CONFIG_RCU_LAZY)) {
pr_alert("CONFIG_RCU_LAZY is disabled, falling back to kfree_rcu() for delayed RCU kfree'ing\n");
kfree_by_call_rcu = 0;
}
if (kfree_by_call_rcu) {
/* do a test to check the timeout. */
orig_jif = rcu_lazy_get_jiffies_till_flush();
rcu_lazy_set_jiffies_till_flush(2 * HZ);
rcu_barrier();
jif_start = jiffies;
jiffies_at_lazy_cb = 0;
call_rcu(&lazy_test1_rh, call_rcu_lazy_test1);
smp_cond_load_relaxed(&rcu_lazy_test1_cb_called, VAL == 1);
rcu_lazy_set_jiffies_till_flush(orig_jif);
if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start < 2 * HZ)) {
pr_alert("ERROR: call_rcu() CBs are not being lazy as expected!\n");
WARN_ON_ONCE(1);
return -1;
}
if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start > 3 * HZ)) {
pr_alert("ERROR: call_rcu() CBs are being too lazy!\n");
WARN_ON_ONCE(1);
return -1;
}
}
kfree_nrealthreads = compute_real(kfree_nthreads);
/* Start up the kthreads. */
@ -784,7 +845,9 @@ kfree_scale_init(void)
schedule_timeout_uninterruptible(1);
}
pr_alert("kfree object size=%zu\n", kfree_mult * sizeof(struct kfree_obj));
pr_alert("kfree object size=%zu, kfree_by_call_rcu=%d\n",
kfree_mult * sizeof(struct kfree_obj),
kfree_by_call_rcu);
kfree_reader_tasks = kcalloc(kfree_nrealthreads, sizeof(kfree_reader_tasks[0]),
GFP_KERNEL);