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Message-ID: <20150128141611.GA2701@tinar>
Date: Wed, 28 Jan 2015 19:46:11 +0530
From: Tina Ruchandani <ruchandani.tina@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Arnd Bergmann <arnd@...db.de>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>
Subject: [PATCH v4] trace: Use 64-bit timekeeping
The ring_buffer_producer uses 'struct timeval' to measure
its start and end times. 'struct timeval' on 32-bit systems
will have its tv_sec value overflow in year 2038 and beyond.
This patch replaces struct timeval with 'ktime_t' which uses
64-bit representation for nanoseconds.
Suggested-by: Arnd Bergmann <arnd@...db.de>
Suggested-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Tina Ruchandani <ruchandani.tina@...il.com>
---
Changes in v4:
- Fix typo in commit message.
- Avoid typecast to 'long long' by defining RUN_TIME as '10ULL'
instead of '10'.
Changes in v3:
- Use a more efficient way to compute condition for exiting loop.
- Fix variable naming - all caps is only for macros.
Changes in v2:
- Use ktime_t instead of timespec64 for efficiency reasons.
---
kernel/trace/ring_buffer_benchmark.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index 3f9e328..13d945c 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -7,7 +7,7 @@
#include <linux/completion.h>
#include <linux/kthread.h>
#include <linux/module.h>
-#include <linux/time.h>
+#include <linux/ktime.h>
#include <asm/local.h>
struct rb_page {
@@ -17,7 +17,7 @@ struct rb_page {
};
/* run time and sleep time in seconds */
-#define RUN_TIME 10
+#define RUN_TIME 10ULL
#define SLEEP_TIME 10
/* number of events for writer to wake up the reader */
@@ -212,8 +212,7 @@ static void ring_buffer_consumer(void)
static void ring_buffer_producer(void)
{
- struct timeval start_tv;
- struct timeval end_tv;
+ ktime_t start_time, end_time, timeout;
unsigned long long time;
unsigned long long entries;
unsigned long long overruns;
@@ -227,7 +226,8 @@ static void ring_buffer_producer(void)
* make the system stall)
*/
trace_printk("Starting ring buffer hammer\n");
- do_gettimeofday(&start_tv);
+ start_time = ktime_get();
+ timeout = ktime_add_ns(start_time, RUN_TIME * NSEC_PER_SEC);
do {
struct ring_buffer_event *event;
int *entry;
@@ -244,7 +244,7 @@ static void ring_buffer_producer(void)
ring_buffer_unlock_commit(buffer, event);
}
}
- do_gettimeofday(&end_tv);
+ end_time = ktime_get();
cnt++;
if (consumer && !(cnt % wakeup_interval))
@@ -264,7 +264,7 @@ static void ring_buffer_producer(void)
cond_resched();
#endif
- } while (end_tv.tv_sec < (start_tv.tv_sec + RUN_TIME) && !kill_test);
+ } while (ktime_before(end_time, timeout) && !kill_test);
trace_printk("End ring buffer hammer\n");
if (consumer) {
@@ -280,9 +280,7 @@ static void ring_buffer_producer(void)
wait_for_completion(&read_done);
}
- time = end_tv.tv_sec - start_tv.tv_sec;
- time *= USEC_PER_SEC;
- time += (long long)((long)end_tv.tv_usec - (long)start_tv.tv_usec);
+ time = ktime_us_delta(end_time, start_time);
entries = ring_buffer_entries(buffer);
overruns = ring_buffer_overruns(buffer);
--
2.2.0.rc0.207.ga3a616c
--
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