Question

我阅读了perf list的手册，并找到PMU的以下memory load/store事件定义：

mem-loads OR cpu/mem-loads/                        [Kernel PMU event]
mem-stores OR cpu/mem-stores/                      [Kernel PMU event]

但我总是阅读使用＆＃34; perf＆＃34;的cpu/mem-loads/pp脚本。而不是＆＃34; cpu/mem-loads/＆＃34;。他们之间有什么区别？它们是一样的吗？我试图谷歌答案，但无法找到解释。

Answer 1

p修饰符代表precise level进行采样时，它用于指示您可以容忍的滑动：从生成样本的有效指令报告指令的距离。 pp表示请求SAMPLE_IP有0个滑动。换句话说，当您进行内存访问采样时，您希望确切地知道哪条指令生成了访问权。

请参阅man perf list：

p - precise level
....
       The p modifier can be used for specifying how precise the instruction address should be. The p modifier can be specified multiple times:

           0 - SAMPLE_IP can have arbitrary skid
           1 - SAMPLE_IP must have constant skid
           2 - SAMPLE_IP requested to have 0 skid
           3 - SAMPLE_IP must have 0 skid

       For Intel systems precise event sampling is implemented with PEBS which supports up to precise-level 2.

       On AMD systems it is implemented using IBS (up to precise-level 2). The precise modifier works with event types 0x76 (cpu-cycles, CPU clocks not halted) and 0xC1 (micro-ops
       retired). Both events map to IBS execution sampling (IBS op) with the IBS Op Counter Control bit (IbsOpCntCtl) set respectively (see AMD64 Architecture Programmer’s Manual Volume
       2: System Programming, 13.3 Instruction-Based Sampling). Examples to use IBS:

           perf record -a -e cpu-cycles:p ...    # use ibs op counting cycles
           perf record -a -e r076:p ...          # same as -e cpu-cycles:p
           perf record -a -e r0C1:p ...          # use ibs op counting micro-ops

“cpu / mem-loads / pp”和“cpu / mem-loads /”有什么区别？

1 个答案: