Messages in this thread | | | Date | Mon, 20 Jun 2022 12:49:57 +0100 | From | Jonathan Cameron <> | Subject | Re: [PATCH v1 1/3] docs: perf: Add description for Alibaba's T-Head PMU driver |
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On Fri, 17 Jun 2022 19:18:23 +0800 Shuai Xue <xueshuai@linux.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@linux.alibaba.com>
Hi Shuia Xue,
A few quick comments inline,
Thanks,
Jonathan
> --- > .../admin-guide/perf/alibaba_pmu.rst | 94 +++++++++++++++++++ > Documentation/admin-guide/perf/index.rst | 1 + > 2 files changed, 95 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..337f4f1d4c54 > --- /dev/null > +++ b/Documentation/admin-guide/perf/alibaba_pmu.rst > @@ -0,0 +1,94 @@ > +============================================================= > +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 > +========================================= > + > +The Yitian 710 SoC supports the most advanced DDR5/4 DRAM to provide > +tremendous memory bandwidth for cloud computing and HPC. The Driveway is a > +module which is a bridge between a router of mesh network and memory > +controller. It provides various functions like secure control, address map > +and so on.
I'd focus on the PMU aspect. No point in describing other features in this document.
> + > +Yitian 710 employs eight DDR5/4 channels, four on each die. Each channel is > +independent of others to service system memory requests. And one DDR5
Each DDR5 channel...
> +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. > + > +Example usage of counting memory data bandwidth:: > + > + perf stat \ > + -e ali_drw_21000/perf_hif_wr/ \
What does hif stand for? Also, perf seems redundant for a perf event.
> + -e ali_drw_21000/perf_hif_rd/ \ > + -e ali_drw_21000/perf_hif_rmw/ \ > + -e ali_drw_21000/perf_cycle/ \ > + -e ali_drw_21080/perf_hif_wr/ \ > + -e ali_drw_21080/perf_hif_rd/ \ > + -e ali_drw_21080/perf_hif_rmw/ \ > + -e ali_drw_21080/perf_cycle/ \ > + -e ali_drw_23000/perf_hif_wr/ \ > + -e ali_drw_23000/perf_hif_rd/ \ > + -e ali_drw_23000/perf_hif_rmw/ \ > + -e ali_drw_23000/perf_cycle/ \ > + -e ali_drw_23080/perf_hif_wr/ \ > + -e ali_drw_23080/perf_hif_rd/ \ > + -e ali_drw_23080/perf_hif_rmw/ \ > + -e ali_drw_23080/perf_cycle/ \ > + -e ali_drw_25000/perf_hif_wr/ \ > + -e ali_drw_25000/perf_hif_rd/ \ > + -e ali_drw_25000/perf_hif_rmw/ \ > + -e ali_drw_25000/perf_cycle/ \ > + -e ali_drw_25080/perf_hif_wr/ \ > + -e ali_drw_25080/perf_hif_rd/ \ > + -e ali_drw_25080/perf_hif_rmw/ \ > + -e ali_drw_25080/perf_cycle/ \ > + -e ali_drw_27000/perf_hif_wr/ \ > + -e ali_drw_27000/perf_hif_rd/ \ > + -e ali_drw_27000/perf_hif_rmw/ \ > + -e ali_drw_27000/perf_cycle/ \ > + -e ali_drw_27080/perf_hif_wr/ \ > + -e ali_drw_27080/perf_hif_rd/ \ > + -e ali_drw_27080/perf_hif_rmw/ \ > + -e ali_drw_27080/perf_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..bf466ae91c6c 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 > + thead_pmu
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