Linux Performance - Perf Event
Created by: Mr Dk.
2023 / 09 / 18 12:55 💣
Hangzhou, Zhejiang, China
Background
Linux 内核提供 perf_event 子系统，其对应的前端工具被称为 perf。这是一个强大的性能剖析工具，跟随内核版本被不断更新、加强。perf 利用了 Linux 内核中的大量性能计数器，支持对某个特定线程/进程、每个特定 CPU、每种事件单独计数；也利用了 Tracepoints，即内核代码中特定位置的钩子（Hook），可以执行动态注册的函数（Probe）。
Events
perf 支持对一系列可衡量的事件进行观测，从中可以洞悉程序的热点代码和性能问题。这些事件的来源有：
- Software Event：来自于 Linux 内核代码中的计数器，比如上下文切换次数
- PMU (Performance Monitoring Unit) Hardware Event：每种处理器内的性能计数器，比如 L1 缓存 miss 次数
- Hardware Cache Event：不同 CPU 的共性性能指标，可能会映射到不同 CPU 的不同硬件计数器上，或干脆不可用
- Tracepoint Event
$ perf list
List of pre-defined events (to be used in -e):
branch-misses [Hardware event]
bus-cycles [Hardware event]
cache-misses [Hardware event]
cache-references [Hardware event]
cpu-cycles OR cycles [Hardware event]
instructions [Hardware event]
stalled-cycles-backend OR idle-cycles-backend [Hardware event]
stalled-cycles-frontend OR idle-cycles-frontend [Hardware event]
alignment-faults [Software event]
bpf-output [Software event]
context-switches OR cs [Software event]
cpu-clock [Software event]
cpu-migrations OR migrations [Software event]
dummy [Software event]
emulation-faults [Software event]
major-faults [Software event]
minor-faults [Software event]
page-faults OR faults [Software event]
task-clock [Software event]
duration_time [Tool event]
L1-dcache-load-misses [Hardware cache event]
L1-dcache-loads [Hardware cache event]
L1-icache-load-misses [Hardware cache event]
L1-icache-loads [Hardware cache event]
LLC-load-misses [Hardware cache event]
LLC-loads [Hardware cache event]
branch-load-misses [Hardware cache event]
branch-loads [Hardware cache event]
dTLB-load-misses [Hardware cache event]
dTLB-loads [Hardware cache event]
iTLB-load-misses [Hardware cache event]
iTLB-loads [Hardware cache event]
ali_drw_21000/chi_rxdat/ [Kernel PMU event]
ali_drw_21000/chi_rxrsp/ [Kernel PMU event]
References
Kernel Wiki - perf: Linux profiling with performance counters