[dpdk-dev] [PATCH v4 3/3] test/rwlock: amortize the cost of getting time

[Joyce Kong <joyce.kong@arm.com>]

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

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

Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Ola Liljedahl <ola.liljedahl@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
 app/test/test_rwlock.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/app/test/test_rwlock.c b/app/test/test_rwlock.c
index f1c5f40..48291c2 100644
--- a/app/test/test_rwlock.c
+++ b/app/test/test_rwlock.c
@@ -86,9 +86,9 @@ test_rwlock_per_core(__attribute__((unused)) void *arg)
 
 static rte_rwlock_t lk = RTE_RWLOCK_INITIALIZER;
 static volatile uint64_t rwlock_data;
-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
 #define TEST_RWLOCK_DEBUG 0
 
 static int
@@ -105,7 +105,7 @@ load_loop_fn(__attribute__((unused)) void *arg)
 			;
 
 	begin = rte_rdtsc_precise();
-	while (time_diff < hz * TIME_MS / 1000) {
+	while (lcount < MAX_LOOP) {
 		rte_rwlock_write_lock(&lk);
 		++rwlock_data;
 		rte_rwlock_write_unlock(&lk);
@@ -119,10 +119,10 @@ load_loop_fn(__attribute__((unused)) void *arg)
 		lcount++;
 		/* delay to make lock duty cycle slightly realistic */
 		rte_pause();
-		time_diff = rte_rdtsc_precise() - begin;
 	}
 
-	lock_count[lcore] = lcount;
+	time_diff = rte_rdtsc_precise() - begin;
+	time_count[lcore] = time_diff * 1000000 / hz;
 	return 0;
 }
 
@@ -146,11 +146,13 @@ test_rwlock_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);
+	memset(time_count, 0, sizeof(time_count));
 
 	return 0;
 }
-- 
2.7.4