[PATCH rcu-dev] rcuperf: Measure memory footprint during kfree_rcu() test

["Joel Fernandes (Google)" <joel@joelfernandes.org>]

During changes to kfree_rcu() code, we often check how much is free
memory. Instead of doing so manually, add a measurement in the test
itself. We measure 4 times during the test for available memory and
compare with the beginning.

A sample run shows something like:

Total time taken by all kfree'ers: 6369738407 ns, loops: 10000, batches: 764 memory footprint:216MB

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>


---
Cc: bristot@redhat.com
Cc: frextrite@gmail.com
Cc: madhuparnabhowmik04@gmail.com
Cc: urezki@gmail.com

 kernel/rcu/rcuperf.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
index da94b89cd531..bf8e9d9b532c 100644
--- a/kernel/rcu/rcuperf.c
+++ b/kernel/rcu/rcuperf.c
@@ -12,6 +12,7 @@
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
+#include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/kthread.h>
 #include <linux/err.h>
@@ -611,12 +612,14 @@ kfree_perf_thread(void *arg)
 	long me = (long)arg;
 	struct kfree_obj *alloc_ptr;
 	u64 start_time, end_time;
+	long mem_begin, mem_during = 0;
 
 	VERBOSE_PERFOUT_STRING("kfree_perf_thread task started");
 	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 	set_user_nice(current, MAX_NICE);
 
 	start_time = ktime_get_mono_fast_ns();
+	mem_begin = si_mem_available();
 
 	if (atomic_inc_return(&n_kfree_perf_thread_started) >= kfree_nrealthreads) {
 		if (gp_exp)
@@ -626,7 +629,14 @@ kfree_perf_thread(void *arg)
 	}
 
 	do {
+		if (!mem_during) {
+			mem_during = mem_begin = si_mem_available();
+		} else if (loop % (kfree_loops / 4) == 0) {
+			mem_during = (mem_during + si_mem_available()) / 2;
+		}
+
 		for (i = 0; i < kfree_alloc_num; i++) {
+
 			alloc_ptr = kmalloc(sizeof(struct kfree_obj), GFP_KERNEL);
 			if (!alloc_ptr)
 				return -ENOMEM;
@@ -645,9 +655,11 @@ kfree_perf_thread(void *arg)
 		else
 			b_rcu_gp_test_finished = cur_ops->get_gp_seq();
 
-		pr_alert("Total time taken by all kfree'ers: %llu ns, loops: %d, batches: %ld\n",
+		pr_alert("Total time taken by all kfree'ers: %llu ns, loops: %d, batches: %ld, memory footprint: %ldMB\n",
 		       (unsigned long long)(end_time - start_time), kfree_loops,
-		       rcuperf_seq_diff(b_rcu_gp_test_finished, b_rcu_gp_test_started));
+		       rcuperf_seq_diff(b_rcu_gp_test_finished, b_rcu_gp_test_started),
+		       (mem_begin - mem_during) >> (20 - PAGE_SHIFT));
+
 		if (shutdown) {
 			smp_mb(); /* Assign before wake. */
 			wake_up(&shutdown_wq);
-- 
2.24.1.735.g03f4e72817-goog