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

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

[Joel Fernandes (Google)]

From: Joel Fernandes <joelaf@google.com>

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

Cc: urezki@gmail.com
Signed-off-by: Joel Fernandes <joelaf@google.com>

---
 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

[PATCH 2/2] rcuperf: Measure memory footprint during kfree_rcu() test (v4)

[Joel Fernandes (Google)]

During changes to kfree_rcu() code, we often check the amount of free
memory.  As an alternative to checking this manually, this commit adds a
measurement in the test itself.  It measures four times during the test
for available memory, digitally filters these measurements to produce a
running average with a weight of 0.5, and compares this digitally
filtered value with the amount of available memory at the beginning of
the test.

We apply the digital filter only once we are more than 25% into the
test. At the 25% mark, we just read available memory and don't apply any
filtering. This prevents the first sample from skewing the results
as we would not consider memory readings that were before memory was
allocated.

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>

---
v1->v2: Minor corrections
v1->v3: Use long long to prevent 32-bit system's overflow
	Handle case where some threads start later than others.
	Start measuring only once 25% into the test. Slightly more accurate.
v3->v4: Simplified test more. Using simple average.

 kernel/rcu/rcuperf.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
index 1fd0cc72022e..c41f009acbbb 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>
@@ -616,14 +617,17 @@ 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
 
+long long mem_begin;
+
 static int
 kfree_perf_thread(void *arg)
 {
 	int i, loop = 0;
 	long me = (long)arg;
 	void *alloc_ptr;
-
 	u64 start_time, end_time;
+	long mem_samples = 0;
+	long long mem_during = 0;
 
 	VERBOSE_PERFOUT_STRING("kfree_perf_thread task started");
 	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
@@ -638,7 +642,17 @@ kfree_perf_thread(void *arg)
 			b_rcu_gp_test_started = cur_ops->get_gp_seq();
 	}
 
+	// Prevent "% 0" error below.
+	if (kfree_loops < 4)
+		kfree_loops = 4;
+
 	do {
+		// Start measuring only from when we are at least 25% into the test.
+		if ((loop != 0) && (loop % (kfree_loops / 4) == 0)) {
+			mem_during = mem_during + si_mem_available();
+			mem_samples++;
+		}
+
 		for (i = 0; i < kfree_alloc_num; i++) {
 			int kfree_type = i % 4;
 
@@ -671,6 +685,8 @@ kfree_perf_thread(void *arg)
 		cond_resched();
 	} while (!torture_must_stop() && ++loop < kfree_loops);
 
+	mem_during = (mem_during / mem_samples);
+
 	if (atomic_inc_return(&n_kfree_perf_thread_ended) >= kfree_nrealthreads) {
 		end_time = ktime_get_mono_fast_ns();
 
@@ -679,9 +695,13 @@ 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",
+		// The "memory footprint" field represents how much in-flight
+		// memory is allocated during the test and waiting to be freed.
+		pr_alert("Total time taken by all kfree'ers: %llu ns, loops: %d, batches: %ld, memory footprint: %lldMB\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);
@@ -753,6 +773,8 @@ kfree_perf_init(void)
 		goto unwind;
 	}
 
+	mem_begin = si_mem_available();
+
 	for (i = 0; i < kfree_nrealthreads; i++) {
 		firsterr = torture_create_kthread(kfree_perf_thread, (void *)i,
 						  kfree_reader_tasks[i]);
-- 
2.25.0.rc1.283.g88dfdc4193-goog

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

[Uladzislau Rezki]

Hello, Joel.

> This patch varies the allocated size of objects to be more realistic in
> comparison to production workloads.
> 
> Cc: urezki@gmail.com
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> 
> ---
>  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
> 

Good point and patch!

Tested-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Vlad Rezki

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

[Joel Fernandes (Google)]

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

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

---
 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