Commit 084e04ff authored by Joel Fernandes (Google)'s avatar Joel Fernandes (Google) Committed by Paul E. McKenney
Browse files

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: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent c945b4da

kernel/rcu/rcuscale.c

+65 −2
Original line number Diff line number Diff line
@@ -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);