Re: [PATCH 3/3] drivers/perf: hisi: Add TLP filter support

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Tue, 25 Oct 2022 19:32:42 +0800
Yicong Yang <yangyicong@huawei.com> wrote:

> From: Yicong Yang <yangyicong@hisilicon.com>
> 
> The PMU support to filter the TLP when counting the bandwidth with below
> options:
> 
> - only count the TLP headers
> - only count the TLP payloads
> - count both TLP headers and payloads
> 
> In the current driver it's default to count the TLP payloads only, which
> will have an implicity side effects that on the traffic only have header
> only TLPs, we'll get no data.
> 
> Make this user configuration through "len_mode" parameter and make it
> default to count both TLP headers and payloads when user not specified.
> Also update the documentation for it.

I suppose this filter option is useful.   Default of "both" makes sense.

A few minor suggestions inline.

Jonathan

> 
> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
> ---
>  .../admin-guide/perf/hisi-pcie-pmu.rst        | 20 +++++++++++++++++++
>  drivers/perf/hisilicon/hisi_pcie_pmu.c        | 14 ++++++++++++-
>  2 files changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/perf/hisi-pcie-pmu.rst b/Documentation/admin-guide/perf/hisi-pcie-pmu.rst
> index bbe66480ff85..83a2ef11b1a0 100644
> --- a/Documentation/admin-guide/perf/hisi-pcie-pmu.rst
> +++ b/Documentation/admin-guide/perf/hisi-pcie-pmu.rst
> @@ -104,3 +104,23 @@ when TLP length < threshold.
>  Example usage of perf::
>  
>    $# perf stat -e hisi_pcie0_core0/rx_mrd_flux,thr_len=0x4,thr_mode=1/ sleep 5
> +
> +4. TLP Length filter
> +When counting bandwidth, the data can be composed of certain parts of TLP
> +packets. You can specify it through "len_mode":
> +
> +- 2'b00: Reserved (Do not use this since the behaviour is undefined)
> +- 2'b01: Bandwidth of TLP payloads
> +- 2'b10: Bandwidth of TLP headers
> +- 2'b11: Bandwidth of both TLP payloads and headers

We could describe this as a bitmap, but i think you are right in thinking
it is clearer to present it as 3 values as not always obvious that the bitmap
is controlling sum of two different things.

> +
> +For example, "len_mode=2" means only counting the bandwidth of TLP headers
> +and "len_mode=3" means the final bandwidth data is composed of both TLP
> +headers and payloads. You need to carefully using this to avoid losing
> +data.

I'm not sure this warning makes sense.  If user has set this filter then
they don't want to measure the types they haven't picked.  I would drop
the warning and example.  It is fairly obvious that no_counts == nothing
to count.
 
> For example you're likely to get no counts by "len_mode=1" if the TLPs
> +on the traffic has no payload.
Drop this example.

> This config is optional, by default it'll
> +be 2'b11.

Anything with a default is inherently optional, so could we just say
Default value if not specified is 2'b11.

> +
> +Example usage of perf::
> +
> +  $# perf stat -e hisi_pcie0_core0/rx_mrd_flux,len_mode=0x1/ sleep 5
> diff --git a/drivers/perf/hisilicon/hisi_pcie_pmu.c b/drivers/perf/hisilicon/hisi_pcie_pmu.c
> index 071e63d9a9ac..6fee0b6e163b 100644
> --- a/drivers/perf/hisilicon/hisi_pcie_pmu.c
> +++ b/drivers/perf/hisilicon/hisi_pcie_pmu.c
> @@ -47,10 +47,14 @@
>  #define HISI_PCIE_EVENT_M		GENMASK_ULL(15, 0)
>  #define HISI_PCIE_THR_MODE_M		GENMASK_ULL(27, 27)
>  #define HISI_PCIE_THR_M			GENMASK_ULL(31, 28)
> +#define HISI_PCIE_LEN_M			GENMASK_ULL(35, 34)
>  #define HISI_PCIE_TARGET_M		GENMASK_ULL(52, 36)
>  #define HISI_PCIE_TRIG_MODE_M		GENMASK_ULL(53, 53)
>  #define HISI_PCIE_TRIG_M		GENMASK_ULL(59, 56)
>  
> +/* Default config of TLP length mode, will count both TLP headers and payloads */
> +#define HISI_PCIE_LEN_M_DEFAULT		3ULL
> +
>  #define HISI_PCIE_MAX_COUNTERS		8
>  #define HISI_PCIE_REG_STEP		8
>  #define HISI_PCIE_THR_MAX_VAL		10
> @@ -91,6 +95,7 @@ HISI_PCIE_PMU_FILTER_ATTR(thr_len, config1, 3, 0);
>  HISI_PCIE_PMU_FILTER_ATTR(thr_mode, config1, 4, 4);
>  HISI_PCIE_PMU_FILTER_ATTR(trig_len, config1, 8, 5);
>  HISI_PCIE_PMU_FILTER_ATTR(trig_mode, config1, 9, 9);
> +HISI_PCIE_PMU_FILTER_ATTR(len_mode, config1, 11, 10);
>  HISI_PCIE_PMU_FILTER_ATTR(port, config2, 15, 0);
>  HISI_PCIE_PMU_FILTER_ATTR(bdf, config2, 31, 16);
>  
> @@ -215,8 +220,8 @@ static void hisi_pcie_pmu_config_filter(struct perf_event *event)
>  {
>  	struct hisi_pcie_pmu *pcie_pmu = to_pcie_pmu(event->pmu);
>  	struct hw_perf_event *hwc = &event->hw;
> +	u64 port, trig_len, thr_len, len_mode;
>  	u64 reg = HISI_PCIE_INIT_SET;
> -	u64 port, trig_len, thr_len;
>  
>  	/* Config HISI_PCIE_EVENT_CTRL according to event. */
>  	reg |= FIELD_PREP(HISI_PCIE_EVENT_M, hisi_pcie_get_real_event(event));
> @@ -245,6 +250,12 @@ static void hisi_pcie_pmu_config_filter(struct perf_event *event)
>  		reg |= HISI_PCIE_THR_EN;
>  	}
>  
> +	len_mode = hisi_pcie_get_len_mode(event);
> +	if (len_mode)
> +		reg |= FIELD_PREP(HISI_PCIE_LEN_M, len_mode);
> +	else
> +		reg |= FIELD_PREP(HISI_PCIE_LEN_M, HISI_PCIE_LEN_M_DEFAULT);
> +
>  	hisi_pcie_pmu_writeq(pcie_pmu, HISI_PCIE_EVENT_CTRL, hwc->idx, reg);
>  }
>  
> @@ -711,6 +722,7 @@ static struct attribute *hisi_pcie_pmu_format_attr[] = {
>  	HISI_PCIE_PMU_FORMAT_ATTR(thr_mode, "config1:4"),
>  	HISI_PCIE_PMU_FORMAT_ATTR(trig_len, "config1:5-8"),
>  	HISI_PCIE_PMU_FORMAT_ATTR(trig_mode, "config1:9"),
> +	HISI_PCIE_PMU_FORMAT_ATTR(len_mode, "config1:10-11"),
>  	HISI_PCIE_PMU_FORMAT_ATTR(port, "config2:0-15"),
>  	HISI_PCIE_PMU_FORMAT_ATTR(bdf, "config2:16-31"),
>  	NULL