首先要确定使用的系统里有arm_smmuv3_pmu这个模块，或者它已经被编译进内核。
这个模块的代码在内核目录kernel/drivers/perf/arm_smmuv3_pmu.c, 内核配置是:
CONFIG_ARM_SMMU_V3_PMU确定使用的单板上的UEFI里有你要测试的模块对应的SMMU PMCG节点，没有这个节点的
的话即使加载上面的驱动也无法使用SMMU PMCG正常使用的话，dmesg | grep pmcg可以看见类似信息:
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17Ubuntu:/ # dmesg | grep pmcg
[ 1232.379951] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.8.auto: option mask 0x1
[ 1232.380040] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.8.auto: Registered PMU @ 0x0000000148020000 using 8 counters with Individual filter settings
[ 1232.380094] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.9.auto: option mask 0x1
[ 1232.380142] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.9.auto: Registered PMU @ 0x0000000201020000 using 8 counters with Individual filter settings
[ 1232.380190] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.10.auto: option mask 0x1
[ 1232.380241] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.10.auto: Registered PMU @ 0x0000000100020000 using 8 counters with Individual filter settings
[ 1232.380286] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.11.auto: option mask 0x1
[ 1232.380337] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.11.auto: Registered PMU @ 0x0000000140020000 using 8 counters with Individual filter settings
[ 1232.380397] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.12.auto: option mask 0x1
[ 1232.380445] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.12.auto: Registered PMU @ 0x0000200148020000 using 8 counters with Individual filter settings
[ 1232.380491] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.13.auto: option mask 0x1
[ 1232.380542] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.13.auto: Registered PMU @ 0x0000200201020000 using 8 counters with Individual filter settings
[ 1232.380601] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.14.auto: option mask 0x1
[ 1232.380653] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.14.auto: Registered PMU @ 0x0000200100020000 using 8 counters with Individual filter settings
[ 1232.380698] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.15.auto: option mask 0x1
[ 1232.380770] arm-smmu-v3-pmcg arm-smmu-v3-pmcg.15.auto: Registered PMU @ 0x0000200140020000 using 8 counters with Individual filter settings使用perf list | grep pmcg可以查看系统支持的pmcg相关的时间类型:
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11Ubuntu:/ # perf list | grep pmcg
[...]
smmuv3_pmcg_140020/config_cache_miss/ [Kernel PMU event]
smmuv3_pmcg_140020/config_struct_access/ [Kernel PMU event]
smmuv3_pmcg_140020/cycles/ [Kernel PMU event]
smmuv3_pmcg_140020/pcie_ats_trans_passed/ [Kernel PMU event]
smmuv3_pmcg_140020/pcie_ats_trans_rq/ [Kernel PMU event]
smmuv3_pmcg_140020/tlb_miss/ [Kernel PMU event]
smmuv3_pmcg_140020/trans_table_walk_access/ [Kernel PMU event]
smmuv3_pmcg_140020/transaction/ [Kernel PMU event]
[...]使用pmcg之前需要先明确需要测试的设备是在哪个pmcg之下，pmcg的命名方式是:
smmuv3_pmcg_, 这里的phys_addr_page是对应SMMU PMCG基地址去掉
低12bit。这里的设计有点不好，使用者很难找到对应的关系 :(当想观测一个程序对应的SMMU上统计信息时我们可以, 比如这样:
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perf stat -e smmuv3_pmcg_<phys_addr_page>/tlb_miss/ <your_program>
的到程序执行过程的smmu tlb miss数目。把这里的tlb_miss换成上面perf list | grep pmcg
所示的其他事件，就可以得到其他事件的统计。实际系统上可能一个smmu下接着多个外设，只想看一个外设在smmu上统计数据可以，比如
这样:1
perf stat -e smmuv3_pmcg_<phys_addr_page>/tlb_miss/,filter_enable=1,filter_span=0,filter_stream_id=0x75 <your_program>
上面的0x75是设备对应的stream_id，PCIe设备的话，一般就是这个设备的BDF号。
(fix me: device function number怎么表示?)如果有smmu自定义的event实现，可以指定具体的event编号, 比如:
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perf stat -e smmuv3_pmcg_<phys_addr_page>/event=0x80/ <your_program>
对于自定义的event，定义的命令是：
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perf stat -e smmuv4_pmcg_<phys_addr_page>/event=0x80,filter_enable=1,filter_span=0,filter_stream_id=0x75/ <your_program>
