Linux Kernel Performance

    Linux kernel 的profiling工具有很多，如oprofile，Redhat上则有systemtap，oracle上有从solaris上移植过来的DTrace，还有function trace，最近几年kernel中又出现了一个perf，综合来看perf的前景最为看好，完全可取代oprofile。

    perf是performance的缩写，代码与kernel source code一同发布（弥补了oprofile的遗憾，用户空间程序和kernel程序的分离），经过几年的发展，perf现在已经相当成熟，几乎所有的performance都能满足了。

 

 

[root@localhost perf]# ./perf

 usage: perf [--version] [--help] COMMAND [ARGS]

 The most commonly used perf commands are:
   annotate        Read perf.data (created by perf record) and display annotated code
   archive         Create archive with object files with build-ids found in perf.data file
   bench           General framework for benchmark suites
   buildid-cache   Manage build-id cache.
   buildid-list    List the buildids in a perf.data file
   diff            Read two perf.data files and display the differential profile
   evlist          List the event names in a perf.data file
   inject          Filter to augment the events stream with additional information
   kmem            Tool to trace/measure kernel memory(slab) properties
   kvm             Tool to trace/measure kvm guest os
   list            List all symbolic event types
   lock            Analyze lock events
   probe           Define new dynamic tracepoints
   record          Run a command and record its profile into perf.data
   report          Read perf.data (created by perf record) and display the profile
   sched           Tool to trace/measure scheduler properties (latencies)
   script          Read perf.data (created by perf record) and display trace output
   stat            Run a command and gather performance counter statistics
   test            Runs sanity tests.
   timechart       Tool to visualize total system behavior during a workload
   top             System profiling tool.

 See 'perf help COMMAND' for more information on a specific command.

 

 比较酷的命令如perf top，用过top命令的都知道

还有perf annotate，把汇编和代码都显示出来，还有timechart/kvm等命令，做的的非常好。probe则可检测各种自定义的tracepoints。

 

    基于perf生成的record可做进一步分析，如下面的Flame Graphs，用perl脚本处理record，生成profing图片

Linux Kernel Performance: Flame Graphs

 

 

perf总体来说非常好用（有些命令格式有点复杂），相比oprofile来说，方便不少，起码不用再下载一个用户空间的程序，Linux 3.0以后基本上都把perf编译进去了，但很多production的机器没有把oprofile编进去。