Re: [PATCH 3/5] hwtracing: hisi_ptt: Optimize the trace data committing

Jonathan Cameron
2023-08-25T11:25:49Z

On Wed, 9 Aug 2023 16:18:23 +0800
Yicong Yang <yangyicong@huawei.com> wrote:

> From: Yicong Yang <yangyicong@hisilicon.com>
>
> Currently during the PTT trace, we'll only commit the data
> to the perf core when its full, which means after 4 interrupts
> and totally 16MiB data while the AUX buffer is 16MiB length.
> Then the userspace gets notified and handle the data. The driver
> cannot apply a new AUX buffer immediately until the committed data
> are handled and there's enough room in the buffer again.
>
> This patch tries to optimize this by commit the data in every
> interrupts in a 4MiB granularity. Then the userspace can have
> enough time to consume the data and there's always enough room
> in the AUX buffer.
>
> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>

Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
> drivers/hwtracing/ptt/hisi_ptt.c | 15 +++++++--------
> 1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/hwtracing/ptt/hisi_ptt.c b/drivers/hwtracing/ptt/hisi_ptt.c
> index 89638ed96cf9..3aba7bb6e548 100644
> --- a/drivers/hwtracing/ptt/hisi_ptt.c
> +++ b/drivers/hwtracing/ptt/hisi_ptt.c
> @@ -274,15 +274,14 @@ static int hisi_ptt_update_aux(struct hisi_ptt *hisi_ptt, int index, bool stop)
> buf->pos += size;
>
> /*
> - * Just commit the traced data if we're going to stop. Otherwise if the
> - * resident AUX buffer cannot contain the data of next trace buffer,
> - * apply a new one.
> + * Always commit the data to the AUX buffer in time to make sure
> + * userspace got enough time to consume the data.
> + *
> + * If we're not going to stop, apply a new one and check whether
> + * there's enough room for the next trace.
> */
> - if (stop) {
> - perf_aux_output_end(handle, buf->pos);
> - } else if (buf->length - buf->pos < HISI_PTT_TRACE_BUF_SIZE) {
> - perf_aux_output_end(handle, buf->pos);
> -
> + perf_aux_output_end(handle, size);
> + if (!stop) {
> buf = perf_aux_output_begin(handle, event);
> if (!buf)
> return -EINVAL;