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[PATCH] crc32: use ktime_get_ns for measurement

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The crc32 test function measures the elapsed time in nanoseconds,
but uses 'struct timespec' for that. We want to remove timespec
from the kernel for y2038 compatibility, and ktime_get_ns()
also helps make the code simpler here.

It is also slightly better to use monontonic time, as we
are only interested in the time difference.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 lib/crc32.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

Not sure who'd pick up this patch, both David Miller and Andrew
Morton have taken patches for this file in the past, but nobody
is listed in the maintainers file.

diff --git a/lib/crc32.c b/lib/crc32.c
index 9a907d489d95..7fbd1a112b9d 100644
--- a/lib/crc32.c
+++ b/lib/crc32.c
@@ -979,7 +979,6 @@ static int __init crc32c_test(void)
 	int i;
 	int errors = 0;
 	int bytes = 0;
-	struct timespec start, stop;
 	u64 nsec;
 	unsigned long flags;
 
@@ -999,20 +998,17 @@ static int __init crc32c_test(void)
 	local_irq_save(flags);
 	local_irq_disable();
 
-	getnstimeofday(&start);
+	nsec = ktime_get_ns();
 	for (i = 0; i < 100; i++) {
 		if (test[i].crc32c_le != __crc32c_le(test[i].crc, test_buf +
 		    test[i].start, test[i].length))
 			errors++;
 	}
-	getnstimeofday(&stop);
+	nsec = ktime_get_ns() - nsec;
 
 	local_irq_restore(flags);
 	local_irq_enable();
 
-	nsec = stop.tv_nsec - start.tv_nsec +
-		1000000000 * (stop.tv_sec - start.tv_sec);
-
 	pr_info("crc32c: CRC_LE_BITS = %d\n", CRC_LE_BITS);
 
 	if (errors)
@@ -1065,7 +1061,6 @@ static int __init crc32_test(void)
 	int i;
 	int errors = 0;
 	int bytes = 0;
-	struct timespec start, stop;
 	u64 nsec;
 	unsigned long flags;
 
@@ -1088,7 +1083,7 @@ static int __init crc32_test(void)
 	local_irq_save(flags);
 	local_irq_disable();
 
-	getnstimeofday(&start);
+	nsec = ktime_get_ns();
 	for (i = 0; i < 100; i++) {
 		if (test[i].crc_le != crc32_le(test[i].crc, test_buf +
 		    test[i].start, test[i].length))
@@ -1098,14 +1093,11 @@ static int __init crc32_test(void)
 		    test[i].start, test[i].length))
 			errors++;
 	}
-	getnstimeofday(&stop);
+	nsec = ktime_get_ns() - nsec;
 
 	local_irq_restore(flags);
 	local_irq_enable();
 
-	nsec = stop.tv_nsec - start.tv_nsec +
-		1000000000 * (stop.tv_sec - start.tv_sec);
-
 	pr_info("crc32: CRC_LE_BITS = %d, CRC_BE BITS = %d\n",
 		 CRC_LE_BITS, CRC_BE_BITS);
 
-- 
2.9.0

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[PATCH] crc32: use ktime_get_ns for measurement Arnd Bergmann <arnd@arndb.de> - 2016-06-17 16:40 +0200

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