根据perf教程 ， perf stat应该使用硬件计数器报告caching未命中。 但是，在我的系统上（最新的Arch Linux），它并没有：
[joel@panda goog]$ perf stat ./hash Performance counter stats for './hash': 869.447863 task-clock # 0.997 CPUs utilized 92 context-switches # 0.106 K/sec 4 cpu-migrations # 0.005 K/sec 1,041 page-faults # 0.001 M/sec 2,628,646,296 cycles # 3.023 GHz 819,269,992 stalled-cycles-frontend # 31.17% frontend cycles idle 132,355,435 stalled-cycles-backend # 5.04% backend cycles idle 4,515,152,198 instructions # 1.72 insns per cycle # 0.18 stalled cycles per insn 1,060,739,808 branches # 1220.015 M/sec 2,653,157 branch-misses # 0.25% of all branches 0.871766141 seconds time elapsed
我错过了什么？ 我已经search了手册页和网页，但没有发现任何明显的东西。
编辑：我的CPU是英特尔i5 2300K，如果这件事。
在我的系统上， Intel Xeon X5570 @ 2.93 GHz我能够得到perf stat报告缓存引用和未命中通过明确地要求这些事件
perf stat -B -e cache-references,cache-misses,cycles,instructions,branches,faults,migrations sleep 5 Performance counter stats for 'sleep 5': 10573 cache-references 1949 cache-misses # 18.434 % of all cache refs 1077328 cycles # 0.000 GHz 715248 instructions # 0.66 insns per cycle 151188 branches 154 faults 0 migrations 5.002776842 seconds time elapsed
默认的一组事件不包括缓存事件，匹配你的结果，我不知道为什么
perf stat -B sleep 5 Performance counter stats for 'sleep 5': 0.344308 task-clock # 0.000 CPUs utilized 1 context-switches # 0.003 M/sec 0 CPU-migrations # 0.000 M/sec 154 page-faults # 0.447 M/sec 977183 cycles # 2.838 GHz 586878 stalled-cycles-frontend # 60.06% frontend cycles idle 430497 stalled-cycles-backend # 44.05% backend cycles idle 720815 instructions # 0.74 insns per cycle # 0.81 stalled cycles per insn 152217 branches # 442.095 M/sec 7646 branch-misses # 5.02% of all branches 5.002763199 seconds time elapsed
在最新的源代码中 ，默认事件不再包括cache-misses和cache-references ：
struct perf_event_attr default_attrs[] = { { .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_TASK_CLOCK }, { .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_CONTEXT_SWITCHES }, { .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_CPU_MIGRATIONS }, { .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_PAGE_FAULTS }, { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_CPU_CYCLES }, { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_STALLED_CYCLES_FRONTEND }, { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_STALLED_CYCLES_BACKEND }, { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_INSTRUCTIONS }, { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS }, { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_BRANCH_MISSES }, };
所以这个男人和大多数的网络已经过时了。
我已经花了几分钟的时间去了解perf 。 通过首先记录并报告数据（都包括perf工具），我发现了缓存未命中。
要查看事件列表：
perf list
例如，为了切断最后一级缓存加载失败，您将要使用事件LLC-loads-misses这样的事情
perf record -e LLC-loads-misses ./your_program
然后报告结果
perf report -v