[dpdk-dev] [PATCH v6 2/3] test/spinlock: amortize the cost of getting time

[Gavin Hu <gavin.hu@arm.com>]

Instead of getting timestamps per iteration, amortize its overhead
can help getting more precise benchmarking results.

Fixes: af75078fece3 ("first public release")
Cc: stable@dpdk.org

Signed-off-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Joyce Kong <Joyce.Kong@arm.com>
Reviewed-by: ruifeng wang <ruifeng.wang@arm.com>
Reviewed-by: honnappa nagarahalli <honnappa.nagarahalli@arm.com>
---
 app/test/test_spinlock.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/app/test/test_spinlock.c b/app/test/test_spinlock.c
index 6795195..6ac7495 100644
--- a/app/test/test_spinlock.c
+++ b/app/test/test_spinlock.c
@@ -96,16 +96,16 @@ test_spinlock_recursive_per_core(__attribute__((unused)) void *arg)
 }
 
 static rte_spinlock_t lk = RTE_SPINLOCK_INITIALIZER;
-static uint64_t lock_count[RTE_MAX_LCORE] = {0};
+static uint64_t time_count[RTE_MAX_LCORE] = {0};
 
-#define TIME_MS 100
+#define MAX_LOOP 10000
 
 static int
 load_loop_fn(void *func_param)
 {
 	uint64_t time_diff = 0, begin;
 	uint64_t hz = rte_get_timer_hz();
-	uint64_t lcount = 0;
+	volatile uint64_t lcount = 0;
 	const int use_lock = *(int*)func_param;
 	const unsigned lcore = rte_lcore_id();
 
@@ -114,15 +114,15 @@ load_loop_fn(void *func_param)
 		while (rte_atomic32_read(&synchro) == 0);
 
 	begin = rte_get_timer_cycles();
-	while (time_diff < hz * TIME_MS / 1000) {
+	while (lcount < MAX_LOOP) {
 		if (use_lock)
 			rte_spinlock_lock(&lk);
 		lcount++;
 		if (use_lock)
 			rte_spinlock_unlock(&lk);
-		time_diff = rte_get_timer_cycles() - begin;
 	}
-	lock_count[lcore] = lcount;
+	time_diff = rte_get_timer_cycles() - begin;
+	time_count[lcore] = time_diff * 1000000 / hz;
 	return 0;
 }
 
@@ -136,14 +136,16 @@ test_spinlock_perf(void)
 
 	printf("\nTest with no lock on single core...\n");
 	load_loop_fn(&lock);
-	printf("Core [%u] count = %"PRIu64"\n", lcore, lock_count[lcore]);
-	memset(lock_count, 0, sizeof(lock_count));
+	printf("Core [%u] Cost Time = %"PRIu64" us\n", lcore,
+						time_count[lcore]);
+	memset(time_count, 0, sizeof(time_count));
 
 	printf("\nTest with lock on single core...\n");
 	lock = 1;
 	load_loop_fn(&lock);
-	printf("Core [%u] count = %"PRIu64"\n", lcore, lock_count[lcore]);
-	memset(lock_count, 0, sizeof(lock_count));
+	printf("Core [%u] Cost Time = %"PRIu64" us\n", lcore,
+						time_count[lcore]);
+	memset(time_count, 0, sizeof(time_count));
 
 	printf("\nTest with lock on %u cores...\n", rte_lcore_count());
 
@@ -158,11 +160,12 @@ test_spinlock_perf(void)
 	rte_eal_mp_wait_lcore();
 
 	RTE_LCORE_FOREACH(i) {
-		printf("Core [%u] count = %"PRIu64"\n", i, lock_count[i]);
-		total += lock_count[i];
+		printf("Core [%u] Cost Time = %"PRIu64" us\n", i,
+						time_count[i]);
+		total += time_count[i];
 	}
 
-	printf("Total count = %"PRIu64"\n", total);
+	printf("Total Cost Time = %"PRIu64" us\n", total);
 
 	return 0;
 }
-- 
2.7.4