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

Question

我阅读了perf list的手册，找到了memory load/store的以下PMU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 perf 脚本，它使用“cpu/mem-loads/pp”而不是“cpu/mem-loads/”。它们之间有什么区别？它们是一样的吗？我试过 google 答案，但找不到解释。

Answer 1

修饰符p代表precise level 在做采样的时候，它用来表示你可以容忍的skid：报告的指令距离生成样本的有效指令有多远。 pp 表示要求 SAMPLE_IP 有 0 个打滑。换句话说，当你做内存访问采样时，你想知道到底是哪条指令产生了访问。

参见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？

What is the difference between "cpu/mem-loads/pp" and "cpu/mem-loads/"?

linux

performance

perf