On Tue, 27 Jan 2015 21:25:38 +0530
Tina Ruchandani <ruchandani.t...@gmail.com> wrote:
> 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 seconds
Doesn't ktime_t actually use 64-bit representation for nanoseconds?
>
> Suggested-by: Arnd Bergmann <a...@arndb.de>
> Signed-off-by: Tina Ruchandani <ruchandani.t...@gmail.com>
> ---
> 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 | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/trace/ring_buffer_benchmark.c
> b/kernel/trace/ring_buffer_benchmark.c
> index 3f9e328..0a50abb 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 {
> @@ -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 +226,9 @@ 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,
> + ((long long) RUN_TIME) * NSEC_PER_SEC);
Instead of the (long long) typecast, could you define RUN_TIME as 10ULL.
Makes the code a bit cleaner, and we can put that on one line.
Rest looks fine.
-- Steve
> do {
> struct ring_buffer_event *event;
> int *entry;
> @@ -244,7 +245,7 @@ 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 +265,7 @@ 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 +281,7 @@ 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);
--
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