Merge tag 'trace-tools-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

4fa118e5 · Linus Torvalds <[email protected]> · 2025-03-27 17:03:01 -07:00

Pull tracing tooling updates from Steven Rostedt:

 - Allow RTLA to collect data via BPF

   The current implementation of rtla uses libtracefs and libtraceevent
   to pull sample events generated by the timerlat tracer from the trace
   buffer. rtla then processes the sample by updating the histogram and
   summary (current, maximum, minimum, and sum values) as well as checks
   if tracing has been stopped due to threshold overflow.

   In use cases where a large number of samples is being generated, that
   is, with measurements running on many CPUs and with a low interval,
   this sample processing design causes a significant CPU load on the
   rtla side. Furthermore, with >100 CPUs and 100us interval, rtla was
   reported as not being able to keep up with the samples and dropping
   most of them, leading to it being unusable.

   Change the way the timerlat trace processes samples by attaching a
   BPF program to the trace event using the BPF skeleton feature of
   bpftool. Unlike the current implementation, the BPF implementation
   does not check whether tracing is stopped (in BPF mode, tracing is
   always off to improve performance), but waits for a write to a BPF
   ringbuffer instead. This allows rtla to exit immediately when a
   threshold is violated, without waiting for the next iteration of the
   while loop.

   If the requirements for the BPF implementation are not met, either at
   build time or at run time, the current implementation is used as
   fallback. Which implementation is being used can be seen when running
   rtla timerlat with "-D" option. rtla can be forced to run in non-BPF
   mode by setting the RTLA_NO_BPF option to 1, for debugging purposes.

 - Fix LD_FLAGS from being dropped in build

 - Refactor code to remove duplication of save_trace_to_file

 - Always set options and do not rely on default settings

   Do not rely on the default kernel settings of the tracers when
   starting. They could have been changed by the user which gives
   inconsistent results. Always set the options that rtla expects.

 - Add creation of ctags and TAGS for traversing code

* tag 'trace-tools-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  rtla: Add the ability to create ctags and etags
  rtla/tests: Test setting default options
  rtla/tests: Reset osnoise options before check
  rtla: Always set all tracer options
  rtla/osnoise: Set OSNOISE_WORKLOAD to true
  rtla: Unify apply_config between top and hist
  rtla/osnoise: Unify params struct
  rtla: Fix segfault in save_trace_to_file call
  tools/build: Use SYSTEM_BPFTOOL for system bpftool
  rtla: Refactor save_trace_to_file
  tools/rv: Keep user LDFLAGS in build
  rtla/timerlat: Test BPF mode
  rtla/timerlat_top: Use BPF to collect samples
  rtla/timerlat_top: Move divisor to update
  rtla/timerlat_hist: Use BPF to collect samples
  rtla/timerlat: Add BPF skeleton to collect samples
  rtla: Add optional dependency on BPF tooling
  tools/build: Add bpftool-skeletons feature test
  rtla/timerlat: Unify params struct

Commit

4fa118e5b79fcc537dcb1a860ed319a6106935eb

Parents

744fab2d · 73203269

Merge commit. Changes below are compared with the first parent: 744fab2d.

Changes

25 files changed · +1315 −625