Date:   Wed, 20 Jul 2022 09:41:03 +0800
From:   Shuai Xue <xueshuai@...ux.alibaba.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        will@...nel.org, mark.rutland@....com,
        baolin.wang@...ux.alibaba.com, yaohongbo@...ux.alibaba.com,
        nengchen@...ux.alibaba.com, zhuo.song@...ux.alibaba.com
Subject: Re: [RESEND PATCH v2 1/3] docs: perf: Add description for Alibaba's
 T-Head PMU driver


在 2022/7/19 PM8:35, Jonathan Cameron 写道:
> On Fri, 15 Jul 2022 23:13:08 +0800
> Shuai Xue <xueshuai@...ux.alibaba.com> wrote:
> 
>> Alibaba's T-Head SoC implements uncore PMU for performance and functional
>> debugging to facilitate system maintenance. Document it to provide guidance
>> on how to use it.
>>
>> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
> I'm far from an expert on this, but looks good to me.
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

Thanks for the review.

Cheers,
Shuai


>> ---
>>  .../admin-guide/perf/alibaba_pmu.rst          | 100 ++++++++++++++++++
>>  Documentation/admin-guide/perf/index.rst      |   1 +
>>  2 files changed, 101 insertions(+)
>>  create mode 100644 Documentation/admin-guide/perf/alibaba_pmu.rst
>>
>> diff --git a/Documentation/admin-guide/perf/alibaba_pmu.rst b/Documentation/admin-guide/perf/alibaba_pmu.rst
>> new file mode 100644
>> index 000000000000..11de998bb480
>> --- /dev/null
>> +++ b/Documentation/admin-guide/perf/alibaba_pmu.rst
>> @@ -0,0 +1,100 @@
>> +=============================================================
>> +Alibaba's T-Head SoC Uncore Performance Monitoring Unit (PMU)
>> +=============================================================
>> +
>> +The Yitian 710, custom-built by Alibaba Group's chip development business,
>> +T-Head, implements uncore PMU for performance and functional debugging to
>> +facilitate system maintenance.
>> +
>> +DDR Sub-System Driveway (DRW) PMU Driver
>> +=========================================
>> +
>> +Yitian 710 employs eight DDR5/4 channels, four on each die. Each DDR5 channel
>> +is independent of others to service system memory requests. And one DDR5
>> +channel is split into two independent sub-channels. The DDR Sub-System Driveway
>> +implements separate PMUs for each sub-channel to monitor various performance
>> +metrics.
>> +
>> +The Driveway PMU devices are named as ali_drw_<sys_base_addr> with perf.
>> +For example, ali_drw_21000 and ali_drw_21080 are two PMU devices for two
>> +sub-channels of the same channel in die 0. And the PMU device of die 1 is
>> +prefixed with ali_drw_400XXXXX, e.g. ali_drw_40021000.
>> +
>> +Each sub-channel has 36 PMU counters in total, which is classified into
>> +four groups:
>> +
>> +- Group 0: PMU Cycle Counter. This group has one pair of counters
>> +  pmu_cycle_cnt_low and pmu_cycle_cnt_high, that is used as the cycle count
>> +  based on DDRC core clock.
>> +
>> +- Group 1: PMU Bandwidth Counters. This group has 8 counters that are used
>> +  to count the total access number of either the eight bank groups in a
>> +  selected rank, or four ranks separately in the first 4 counters. The base
>> +  transfer unit is 64B.
>> +
>> +- Group 2: PMU Retry Counters. This group has 10 counters, that intend to
>> +  count the total retry number of each type of uncorrectable error.
>> +
>> +- Group 3: PMU Common Counters. This group has 16 counters, that are used
>> +  to count the common events.
>> +
>> +For now, the Driveway PMU driver only uses counters in group 0 and group 3.
>> +
>> +The DDR Controller (DDRCTL) and DDR PHY combine to create a complete solution
>> +for connecting an SoC application bus to DDR memory devices. The DDRCTL
>> +receives transactions Host Interface (HIF) which is custom-defined by Synopsys.
>> +These transactions are queued internally and scheduled for access while
>> +satisfying the SDRAM protocol timing requirements, transaction priorities, and
>> +dependencies between the transactions. The DDRCTL in turn issues commands on
>> +the DDR PHY Interface (DFI) to the PHY module, which launches and captures data
>> +to and from the SDRAM. The driveway PMUs have hardware logic to gather
>> +statistics and performance logging signals on HIF, DFI, etc.
>> +
>> +By counting the READ, WRITE and RMW commands sent to the DDRC through the HIF
>> +interface, we could calculate the bandwidth. Example usage of counting memory
>> +data bandwidth::
>> +
>> +  perf stat \
>> +    -e ali_drw_21000/hif_wr/ \
>> +    -e ali_drw_21000/hif_rd/ \
>> +    -e ali_drw_21000/hif_rmw/ \
>> +    -e ali_drw_21000/cycle/ \
>> +    -e ali_drw_21080/hif_wr/ \
>> +    -e ali_drw_21080/hif_rd/ \
>> +    -e ali_drw_21080/hif_rmw/ \
>> +    -e ali_drw_21080/cycle/ \
>> +    -e ali_drw_23000/hif_wr/ \
>> +    -e ali_drw_23000/hif_rd/ \
>> +    -e ali_drw_23000/hif_rmw/ \
>> +    -e ali_drw_23000/cycle/ \
>> +    -e ali_drw_23080/hif_wr/ \
>> +    -e ali_drw_23080/hif_rd/ \
>> +    -e ali_drw_23080/hif_rmw/ \
>> +    -e ali_drw_23080/cycle/ \
>> +    -e ali_drw_25000/hif_wr/ \
>> +    -e ali_drw_25000/hif_rd/ \
>> +    -e ali_drw_25000/hif_rmw/ \
>> +    -e ali_drw_25000/cycle/ \
>> +    -e ali_drw_25080/hif_wr/ \
>> +    -e ali_drw_25080/hif_rd/ \
>> +    -e ali_drw_25080/hif_rmw/ \
>> +    -e ali_drw_25080/cycle/ \
>> +    -e ali_drw_27000/hif_wr/ \
>> +    -e ali_drw_27000/hif_rd/ \
>> +    -e ali_drw_27000/hif_rmw/ \
>> +    -e ali_drw_27000/cycle/ \
>> +    -e ali_drw_27080/hif_wr/ \
>> +    -e ali_drw_27080/hif_rd/ \
>> +    -e ali_drw_27080/hif_rmw/ \
>> +    -e ali_drw_27080/cycle/ -- sleep 10
>> +
>> +The average DRAM bandwidth can be calculated as follows:
>> +
>> +- Read Bandwidth =  perf_hif_rd * DDRC_WIDTH * DDRC_Freq / DDRC_Cycle
>> +- Write Bandwidth = (perf_hif_wr + perf_hif_rmw) * DDRC_WIDTH * DDRC_Freq / DDRC_Cycle
>> +
>> +Here, DDRC_WIDTH = 64 bytes.
>> +
>> +The current driver does not support sampling. So "perf record" is
>> +unsupported.  Also attach to a task is unsupported as the events are all
>> +uncore.
>> diff --git a/Documentation/admin-guide/perf/index.rst b/Documentation/admin-guide/perf/index.rst
>> index 69b23f087c05..823db08863db 100644
>> --- a/Documentation/admin-guide/perf/index.rst
>> +++ b/Documentation/admin-guide/perf/index.rst
>> @@ -17,3 +17,4 @@ Performance monitor support
>>     xgene-pmu
>>     arm_dsu_pmu
>>     thunderx2-pmu
>> +   alibaba_pmu

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