The perf tracing tool has evolved quickly. When last we looked, Tom Zanussi had added Python and Perl scripting to perf. Next up would seem to be perf "live mode", where perf no longer requires two steps: record the data, then analyze. Live mode will allow perf trace record and perf trace report to operate via a pipe, which allows instantaneous, as well as continuously updating (a la top), output.

So that no existing perf users need to change their scripts, Zanussi only added the new capabilities when perf recognizes that its record output is going to stdout or report input is coming from stdin. In that case, perf handles the data through a pipe, and uses special synthesized events to provide header information. This will also allow perf to operate over the network by piping its record output to netcat, and then reading it via netcat on another system and piping it into report.

All of the scripts that are installed in the standard perf location (i.e. those which are listed in perf trace -l) are automatically able to be run in live mode:

  $ perf trace syscall-counts

  $ perf trace record syscall-counts -o - | perf trace report syscall-counts -i -

  perf record -c 1 -f -a -M -R -e raw_syscalls:sys_enter -o - | \
  perf trace -i - -s ~/libexec/perf-core/scripts/python/syscall-counts.py

Zanussi also included several sample top-style scripts that can be used to monitor read/write or system call activity updated every three seconds. It looks to be a very useful addition to perf, which is rapidly becoming the "swiss army knife" of kernel monitoring.

Index entries for this article
Kernel	Performance monitoring