rcuscale: Add laziness and kfree tests
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>
diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index 3ef02d4..3baded8 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -95,6 +95,7 @@
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 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 @@
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 @@
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 @@
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);
