Re: [PATCH 1/2] rcuscale: add kfree_rcu() single-argument scale test

[Uladzislau Rezki <urezki@gmail.com>]

On Thu, Feb 04, 2021 at 01:46:48PM -0800, Paul E. McKenney wrote:
> On Fri, Jan 29, 2021 at 09:05:04PM +0100, Uladzislau Rezki (Sony) wrote:
> > To stress and test a single argument of kfree_rcu() call, we
> > should to have a special coverage for it. We used to have it
> > in the test-suite related to vmalloc stressing. The reason is
> > the rcuscale is a correct place for RCU related things.
> > 
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> 
> This is a great addition, but it would be even better if there was
> a way to say "test both in one run".  One way to do this is to have
> torture_param() variables for both kfree_rcu_test_single and (say)
> kfree_rcu_test_double, both bool and both initialized to false.  If both
> have the same value (false or true) both are tested, otherwise only
> the one with value true is tested.  The value of this is that it allows
> testing of both options with one test.
> 
Make sense to me :)

From ba083a543a123455455c81230b7b5a9aa2a9cb7f Mon Sep 17 00:00:00 2001
From: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Date: Fri, 29 Jan 2021 19:51:27 +0100
Subject: [PATCH v2 1/1] rcuscale: add kfree_rcu() single-argument scale test

To stress and test a single argument of kfree_rcu() call, we
should to have a special coverage for it. We used to have it
in the test-suite related to vmalloc stressing. The reason is
the rcuscale is a correct place for RCU related things.

Therefore introduce two torture_param() variables, one is for
single-argument scale test and another one for double-argument
scale test.

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 tested in one run, otherwise only the one with value
true is tested. The value of this is that it allows testing of
both options with one test.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
 kernel/rcu/rcuscale.c | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index 06491d5530db..0cde5c17f06c 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -625,6 +625,8 @@ rcu_scale_shutdown(void *arg)
 torture_param(int, kfree_nthreads, -1, "Number of threads running loops of kfree_rcu().");
 torture_param(int, kfree_alloc_num, 8000, "Number of allocations and frees done in an iteration.");
 torture_param(int, kfree_loops, 10, "Number of loops doing kfree_alloc_num allocations and frees.");
+torture_param(int, kfree_rcu_test_single, 0, "Do we run a kfree_rcu() single-argument scale test?");
+torture_param(int, kfree_rcu_test_double, 0, "Do we run a kfree_rcu() double-argument scale test?");
 
 static struct task_struct **kfree_reader_tasks;
 static int kfree_nrealthreads;
@@ -641,7 +643,7 @@ kfree_scale_thread(void *arg)
 {
 	int i, loop = 0;
 	long me = (long)arg;
-	struct kfree_obj *alloc_ptr;
+	struct kfree_obj *alloc_ptr[2];
 	u64 start_time, end_time;
 	long long mem_begin, mem_during = 0;
 
@@ -665,12 +667,33 @@ kfree_scale_thread(void *arg)
 			mem_during = (mem_during + si_mem_available()) / 2;
 		}
 
+		// 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 tested in one run, otherwise only the one with value
+		// true is tested.
 		for (i = 0; i < kfree_alloc_num; i++) {
-			alloc_ptr = kmalloc(kfree_mult * sizeof(struct kfree_obj), GFP_KERNEL);
-			if (!alloc_ptr)
-				return -ENOMEM;
+			alloc_ptr[0] = kmalloc(kfree_mult * sizeof(struct kfree_obj), GFP_KERNEL);
+			alloc_ptr[1] = (kfree_rcu_test_single == kfree_rcu_test_double) ?
+				kmalloc(kfree_mult * sizeof(struct kfree_obj), GFP_KERNEL) : NULL;
+
+			// 0 ptr. is freed either over single or double argument.
+			if (alloc_ptr[0]) {
+				if (kfree_rcu_test_single == kfree_rcu_test_double ||
+						kfree_rcu_test_single) {
+					kfree_rcu(alloc_ptr[0]);
+				} else {
+					kfree_rcu(alloc_ptr[0], rh);
+				}
+			}
+
+			// 1 ptr. is always freed over double argument.
+			if (alloc_ptr[1])
+				kfree_rcu(alloc_ptr[1], rh);
 
-			kfree_rcu(alloc_ptr, rh);
+			if (!alloc_ptr[0] ||
+					(kfree_rcu_test_single == kfree_rcu_test_double &&
+						!alloc_ptr[1]))
+				return -ENOMEM;
 		}
 
 		cond_resched();
-- 
2.20.1

--
Vlad Rezki