Re: [PATCH 1/8] ntb_perf: Schedule based on time not on performance

[Jiang, Dave]

On Fri, 2016-06-10 at 16:54 -0600, Logan Gunthorpe wrote:
> When debugging performance problems, if some issue causes the ntb
> hardware to be significantly slower than expected, ntb_perf will
> hang requiring a reboot because it only schedules once every 4GB.
> 
> Instead, schedule based on jiffies so it will not hang the CPU if
> the transfer is slow.
> 
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Acked-by: Dave Jiang <dave.jiang@xxxxxxxxx>

> ---
> Âdrivers/ntb/test/ntb_perf.c | 6 ++++--
> Â1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/ntb/test/ntb_perf.c
> b/drivers/ntb/test/ntb_perf.c
> index 4368519..5008ccf 100644
> --- a/drivers/ntb/test/ntb_perf.c
> +++ b/drivers/ntb/test/ntb_perf.c
> @@ -273,6 +273,7 @@ static int perf_move_data(struct pthr_ctx *pctx,
> char __iomem *dst, char *src,
> Â	char __iomem *tmp = dst;
> Â	u64 perf, diff_us;
> Â	ktime_t kstart, kstop, kdiff;
> +	unsigned long last_sleep = jiffies;
> Â
> Â	chunks = div64_u64(win_size, buf_size);
> Â	total_chunks = div64_u64(total, buf_size);
> @@ -288,8 +289,9 @@ static int perf_move_data(struct pthr_ctx *pctx,
> char __iomem *dst, char *src,
> Â		} else
> Â			tmp += buf_size;
> Â
> -		/* Probably should schedule every 4GB to prevent
> soft hang. */
> -		if (((copied % SZ_4G) == 0) && !use_dma) {
> +		/* Probably should schedule every 5s to prevent soft
> hang. */
> +		if (unlikely((jiffies - last_sleep) > 5 * HZ)) {
> +			last_sleep = jiffies;
> Â			set_current_state(TASK_INTERRUPTIBLE);
> Â			schedule_timeout(1);
> Â		}
> --Â
> 2.1.4
>