LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Arnd Bergmann <arnd@arndb.de>
To: "David S . Miller" <davem@davemloft.net>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>, linux-kernel@vger.kernel.org
Subject: [PATCH] crc32: use ktime_get_ns for measurement
Date: Fri, 17 Jun 2016 16:39:18 +0200
Message-ID: <20160617143932.3289626-1-arnd@arndb.de> (raw)

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

                 reply index

Thread overview: [no followups] expand[flat|nested]  mbox.gz  Atom feed

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20160617143932.3289626-1-arnd@arndb.de \
    --to=arnd@arndb.de \
    --cc=akpm@linux-foundation.org \
    --cc=davem@davemloft.net \
    --cc=linux-kernel@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git