[PATCH 1/2] rcuperf: Add support to vary the slab object sizes

["Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx>]

This patch varies the allocated size of objects to be more realistic in
comparison to production workloads.

Cc: urezki@xxxxxxxxx
Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>

---
 kernel/rcu/rcuperf.c | 48 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 41 insertions(+), 7 deletions(-)

diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
index da94b89cd531..1fd0cc72022e 100644
--- a/kernel/rcu/rcuperf.c
+++ b/kernel/rcu/rcuperf.c
@@ -87,6 +87,7 @@ torture_param(bool, shutdown, RCUPERF_SHUTDOWN,
 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() perf test?");
+torture_param(bool, kfree_vary_obj_size, 0, "Vary the kfree_rcu object size");
 
 static char *perf_type = "rcu";
 module_param(perf_type, charp, 0444);
@@ -599,17 +600,29 @@ static int kfree_nrealthreads;
 static atomic_t n_kfree_perf_thread_started;
 static atomic_t n_kfree_perf_thread_ended;
 
-struct kfree_obj {
-	char kfree_obj[8];
-	struct rcu_head rh;
-};
+/*
+ * Define a kfree_obj with size as the @size parameter + the size of rcu_head
+ * (rcu_head is 16 bytes on 64-bit arch).
+ */
+#define DEFINE_KFREE_OBJ(size)	\
+struct kfree_obj_ ## size {	\
+	char kfree_obj[size];	\
+	struct rcu_head rh;	\
+}
+
+/* This should goto the right sized slabs on both 32-bit and 64-bit arch */
+DEFINE_KFREE_OBJ(16); // goes on kmalloc-32 slab
+DEFINE_KFREE_OBJ(32); // goes on kmalloc-64 slab
+DEFINE_KFREE_OBJ(64); // goes on kmalloc-96 slab
+DEFINE_KFREE_OBJ(96); // goes on kmalloc-128 slab
 
 static int
 kfree_perf_thread(void *arg)
 {
 	int i, loop = 0;
 	long me = (long)arg;
-	struct kfree_obj *alloc_ptr;
+	void *alloc_ptr;
+
 	u64 start_time, end_time;
 
 	VERBOSE_PERFOUT_STRING("kfree_perf_thread task started");
@@ -627,11 +640,32 @@ kfree_perf_thread(void *arg)
 
 	do {
 		for (i = 0; i < kfree_alloc_num; i++) {
-			alloc_ptr = kmalloc(sizeof(struct kfree_obj), GFP_KERNEL);
+			int kfree_type = i % 4;
+
+			// Allocate only kfree_obj_16 if rcuperf.kfree_vary_obj_size not passed.
+			if (!kfree_vary_obj_size)
+				kfree_type = 0;
+
+			if (kfree_type == 0)
+				alloc_ptr = kmalloc(sizeof(struct kfree_obj_16), GFP_KERNEL);
+			else if (kfree_type == 1)
+				alloc_ptr = kmalloc(sizeof(struct kfree_obj_32), GFP_KERNEL);
+			else if (kfree_type == 2)
+				alloc_ptr = kmalloc(sizeof(struct kfree_obj_64), GFP_KERNEL);
+			else
+				alloc_ptr = kmalloc(sizeof(struct kfree_obj_96),  GFP_KERNEL);
+
 			if (!alloc_ptr)
 				return -ENOMEM;
 
-			kfree_rcu(alloc_ptr, rh);
+			if (kfree_type == 0)
+				kfree_rcu((struct kfree_obj_16 *)alloc_ptr, rh);
+			else if (kfree_type == 1)
+				kfree_rcu((struct kfree_obj_32 *)alloc_ptr, rh);
+			else if (kfree_type == 2)
+				kfree_rcu((struct kfree_obj_64 *)alloc_ptr, rh);
+			else
+				kfree_rcu((struct kfree_obj_96 *)alloc_ptr, rh);
 		}
 
 		cond_resched();
-- 
2.25.0.rc1.283.g88dfdc4193-goog