The New Linux ’perf’ tools（新的Linux性能的工具）.pdf

The New Linux ’perf’ tools Linux Kongress September, 2010 Arnaldo Carvalho de Melo acme@ Presentation Flow . Motivation . Focus on the tools . But some kernel details will be mentioned . Some demos hopefully at the end How did I get involved? . I am no specialist on performance counters . pahole the dwarves . ELF, DWARF, symtabs, dynsyms, relocations, etc . ftrace How did I get involved? Part two . Part of the Red Hat Real Time team . We need to discover why 100us deadlines are not being met . Why this is slower on your RT kernel than on the RHEL one? . Observability tooling! . Huge educational value, use it! Renewed interest in profiling tools . Complexity of systems growing . Pervasiveness of multithreading . Hardware assists Performance Counters . Performance counters are special hardware registers . Available on most modern CPUs . Count the number of some hw events instructions executed cache-misses suffered branches mispredicted . Without slowing down the kernel or applications . Can trigger interrupts when a number of events have passed Limited resource: Some are programmable, some are for specific events. Processor: UltraSparc 2 Pentium III 2 Athlon 4 IA-64 4 POWER4 8 Pentium IV 18 Nehalem 7 Tracepoints Static probe points that are put in place by subsystem maintainers and that can be enabled later. Dynamic probe points Dynamicly inserted probe points using hardware breakpoints. The oprofile development problem . Disconnected kernel userspace development . Linus problem with Atom and Nehalem support . Less of the 2 broken pieces approach - one working piece . /Articles/339406/ The perf user interface approach . git like . Many subcommands . Per thread/per workload/per CPU