[PATCH v2] mempool: test performance with constant n

[Olivier Matz <olivier.matz@6wind.com>]

From: Morten Brørup <mb@smartsharesystems.com>

"What gets measured gets done."

This patch adds mempool performance tests where the number of objects to
put and get is constant at compile time, which may significantly improve
the performance of these functions. [*]

Also, it is ensured that the array holding the object used for testing
is cache line aligned, for maximum performance.

And finally, the following entries are added to the list of tests:
- Number of kept objects: 512
- Number of objects to get and to put: The number of pointers fitting
  into a cache line, i.e. 8 or 16

[*] Some example performance test (with cache) results:

get_bulk=4 put_bulk=4 keep=128 constant_n=false rate_persec=280480972
get_bulk=4 put_bulk=4 keep=128 constant_n=true  rate_persec=622159462

get_bulk=8 put_bulk=8 keep=128 constant_n=false rate_persec=477967155
get_bulk=8 put_bulk=8 keep=128 constant_n=true  rate_persec=917582643

get_bulk=32 put_bulk=32 keep=32 constant_n=false rate_persec=871248691
get_bulk=32 put_bulk=32 keep=32 constant_n=true rate_persec=1134021836

Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
---

Hi Morten,

Here is the updated patch.

I launched the mempool_perf on my desktop machine, but I don't reproduce the numbers: constant or
non-constant give almost the same rate on my machine (it's even worst with constants). I tested with
your initial patch and with this one. Can you please try this patch, and/or give some details about
your test environment? Here is what I get:

with your patch:
mempool_autotest cache=512 cores=1 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=false rate_persec=152620236
mempool_autotest cache=512 cores=1 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=true rate_persec=144716595
mempool_autotest cache=512 cores=2 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=false rate_persec=306996838
mempool_autotest cache=512 cores=2 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=true rate_persec=287375359
mempool_autotest cache=512 cores=12 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=false rate_persec=977626723
mempool_autotest cache=512 cores=12 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=true rate_persec=963103944

with this patch:
mempool_autotest cache=512 cores=1 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=0 rate_persec=156460646
mempool_autotest cache=512 cores=1 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=1 rate_persec=142173798
mempool_autotest cache=512 cores=2 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=0 rate_persec=312410111
mempool_autotest cache=512 cores=2 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=1 rate_persec=281699942
mempool_autotest cache=512 cores=12 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=0 rate_persec=983315247
mempool_autotest cache=512 cores=12 n_get_bulk=8 n_put_bulk=8 n_keep=128 constant_n=1 rate_persec=950350638


v2:
- use a flag instead of a negative value to enable tests with
  compile-time constant
- use a static inline function instead of a macro
- remove some "noise" (do not change variable type when not required)


Thanks,
Olivier


 app/test/test_mempool_perf.c | 110 ++++++++++++++++++++++++-----------
 1 file changed, 77 insertions(+), 33 deletions(-)

diff --git a/app/test/test_mempool_perf.c b/app/test/test_mempool_perf.c
index 87ad251367..ce7c6241ab 100644
--- a/app/test/test_mempool_perf.c
+++ b/app/test/test_mempool_perf.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: BSD-3-Clause
  * Copyright(c) 2010-2014 Intel Corporation
+ * Copyright(c) 2022 SmartShare Systems
  */

 #include <string.h>
@@ -55,19 +56,24 @@
  *
  *      - Bulk get from 1 to 32
  *      - Bulk put from 1 to 32
+ *      - Bulk get and put from 1 to 32, compile time constant
  *
  *    - Number of kept objects (*n_keep*)
  *
  *      - 32
  *      - 128
+ *      - 512
  */

 #define N 65536
 #define TIME_S 5
 #define MEMPOOL_ELT_SIZE 2048
-#define MAX_KEEP 128
+#define MAX_KEEP 512
 #define MEMPOOL_SIZE ((rte_lcore_count()*(MAX_KEEP+RTE_MEMPOOL_CACHE_MAX_SIZE))-1)

+/* Number of pointers fitting into one cache line. */
+#define CACHE_LINE_BURST (RTE_CACHE_LINE_SIZE / sizeof(uintptr_t))
+
 #define LOG_ERR() printf("test failed at %s():%d\n", __func__, __LINE__)
 #define RET_ERR() do {							\
 		LOG_ERR();						\
@@ -91,6 +97,9 @@ static unsigned n_put_bulk;
 /* number of objects retrieved from mempool before putting them back */
 static unsigned n_keep;

+/* true if we want to test with constant n_get_bulk and n_put_bulk */
+static int use_constant_values;
+
 /* number of enqueues / dequeues */
 struct mempool_test_stats {
 	uint64_t enq_count;
@@ -111,11 +120,43 @@ my_obj_init(struct rte_mempool *mp, __rte_unused void *arg,
 	*objnum = i;
 }

+static __rte_always_inline int
+test_loop(struct rte_mempool *mp, struct rte_mempool_cache *cache,
+	  unsigned int x_keep, unsigned int x_get_bulk, unsigned int x_put_bulk)
+{
+	void *obj_table[MAX_KEEP] __rte_cache_aligned;
+	unsigned int idx;
+	unsigned int i;
+	int ret;
+
+	for (i = 0; likely(i < (N / x_keep)); i++) {
+		/* get x_keep objects by bulk of x_get_bulk */
+		for (idx = 0; idx < x_keep; idx += x_get_bulk) {
+			ret = rte_mempool_generic_get(mp,
+						      &obj_table[idx],
+						      x_get_bulk,
+						      cache);
+			if (unlikely(ret < 0)) {
+				rte_mempool_dump(stdout, mp);
+				return ret;
+			}
+		}
+
+		/* put the objects back by bulk of x_put_bulk */
+		for (idx = 0; idx < x_keep; idx += x_put_bulk) {
+			rte_mempool_generic_put(mp,
+						&obj_table[idx],
+						x_put_bulk,
+						cache);
+		}
+	}
+
+	return 0;
+}
+
 static int
 per_lcore_mempool_test(void *arg)
 {
-	void *obj_table[MAX_KEEP];
-	unsigned i, idx;
 	struct rte_mempool *mp = arg;
 	unsigned lcore_id = rte_lcore_id();
 	int ret = 0;
@@ -139,6 +180,9 @@ per_lcore_mempool_test(void *arg)
 		GOTO_ERR(ret, out);
 	if (((n_keep / n_put_bulk) * n_put_bulk) != n_keep)
 		GOTO_ERR(ret, out);
+	/* for constant n, n_get_bulk and n_put_bulk must be the same */
+	if (use_constant_values && n_put_bulk != n_get_bulk)
+		GOTO_ERR(ret, out);

 	stats[lcore_id].enq_count = 0;

@@ -149,31 +193,23 @@ per_lcore_mempool_test(void *arg)
 	start_cycles = rte_get_timer_cycles();

 	while (time_diff/hz < TIME_S) {
-		for (i = 0; likely(i < (N/n_keep)); i++) {
-			/* get n_keep objects by bulk of n_bulk */
-			idx = 0;
-			while (idx < n_keep) {
-				ret = rte_mempool_generic_get(mp,
-							      &obj_table[idx],
-							      n_get_bulk,
-							      cache);
-				if (unlikely(ret < 0)) {
-					rte_mempool_dump(stdout, mp);
-					/* in this case, objects are lost... */
-					GOTO_ERR(ret, out);
-				}
-				idx += n_get_bulk;
-			}
+		if (!use_constant_values)
+			ret = test_loop(mp, cache, n_keep, n_get_bulk, n_put_bulk);
+		else if (n_get_bulk == 1)
+			ret = test_loop(mp, cache, n_keep, 1, 1);
+		else if (n_get_bulk == 4)
+			ret = test_loop(mp, cache, n_keep, 4, 4);
+		else if (n_get_bulk == CACHE_LINE_BURST)
+			ret = test_loop(mp, cache, n_keep,
+					CACHE_LINE_BURST, CACHE_LINE_BURST);
+		else if (n_get_bulk == 32)
+			ret = test_loop(mp, cache, n_keep, 32, 32);
+		else
+			ret = -1;
+
+		if (ret < 0)
+			GOTO_ERR(ret, out);

-			/* put the objects back */
-			idx = 0;
-			while (idx < n_keep) {
-				rte_mempool_generic_put(mp, &obj_table[idx],
-							n_put_bulk,
-							cache);
-				idx += n_put_bulk;
-			}
-		}
 		end_cycles = rte_get_timer_cycles();
 		time_diff = end_cycles - start_cycles;
 		stats[lcore_id].enq_count += N;
@@ -203,10 +239,10 @@ launch_cores(struct rte_mempool *mp, unsigned int cores)
 	memset(stats, 0, sizeof(stats));

 	printf("mempool_autotest cache=%u cores=%u n_get_bulk=%u "
-	       "n_put_bulk=%u n_keep=%u ",
+	       "n_put_bulk=%u n_keep=%u constant_n=%u ",
 	       use_external_cache ?
 		   external_cache_size : (unsigned) mp->cache_size,
-	       cores, n_get_bulk, n_put_bulk, n_keep);
+	       cores, n_get_bulk, n_put_bulk, n_keep, use_constant_values);

 	if (rte_mempool_avail_count(mp) != MEMPOOL_SIZE) {
 		printf("mempool is not full\n");
@@ -253,9 +289,9 @@ launch_cores(struct rte_mempool *mp, unsigned int cores)
 static int
 do_one_mempool_test(struct rte_mempool *mp, unsigned int cores)
 {
-	unsigned bulk_tab_get[] = { 1, 4, 32, 0 };
-	unsigned bulk_tab_put[] = { 1, 4, 32, 0 };
-	unsigned keep_tab[] = { 32, 128, 0 };
+	unsigned int bulk_tab_get[] = { 1, 4, CACHE_LINE_BURST, 32, 0 };
+	unsigned int bulk_tab_put[] = { 1, 4, CACHE_LINE_BURST, 32, 0 };
+	unsigned int keep_tab[] = { 32, 128, 512, 0 };
 	unsigned *get_bulk_ptr;
 	unsigned *put_bulk_ptr;
 	unsigned *keep_ptr;
@@ -265,13 +301,21 @@ do_one_mempool_test(struct rte_mempool *mp, unsigned int cores)
 		for (put_bulk_ptr = bulk_tab_put; *put_bulk_ptr; put_bulk_ptr++) {
 			for (keep_ptr = keep_tab; *keep_ptr; keep_ptr++) {

+				use_constant_values = 0;
 				n_get_bulk = *get_bulk_ptr;
 				n_put_bulk = *put_bulk_ptr;
 				n_keep = *keep_ptr;
 				ret = launch_cores(mp, cores);
-
 				if (ret < 0)
 					return -1;
+
+				/* replay test with constant values */
+				if (n_get_bulk == n_put_bulk) {
+					use_constant_values = 1;
+					ret = launch_cores(mp, cores);
+					if (ret < 0)
+						return -1;
+				}
 			}
 		}
 	}
--
2.30.2