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

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Message-ID: <8409f208-d976-ef25-07ad-0db693958112@huawei.com>
Date:   Thu, 10 Nov 2022 10:45:37 +0800
From:   Yicong Yang <yangyicong@...wei.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC:     <yangyicong@...ilicon.com>,
        Shaokun Zhang <zhangshaokun@...ilicon.com>,
        <liuqi6124@...il.com>, Jonathan Corbet <corbet@....net>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        John Garry <john.garry@...wei.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-doc@...r.kernel.org>, <linuxarm@...wei.com>,
        <f.fangjian@...wei.com>, <prime.zeng@...wei.com>
Subject: Re: [PATCH 3/3] drivers/perf: hisi: Add TLP filter support

On 2022/11/10 1:09, Jonathan Cameron wrote:
> On Tue, 25 Oct 2022 19:32:42 +0800
> Yicong Yang <yangyicong@...wei.com> wrote:
> 
>> From: Yicong Yang <yangyicong@...ilicon.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@...ilicon.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.
> 

I just to keep the style consistence with the existing doc and yes I also think
it's clearer.

>> +
>> +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.
>  

Just hope users will not make it "len_mode=0" as it's reserved. Will drop it.

>> 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.
> 

ok.

>> 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.
> 

ok, it'll be better.

Will update the doc. Thanks for the comments!

Regards.

>> +
>> +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
> 
> .
>