[0/4] perf lock contention: Improve call stack handling (v2)

Message

Namhyung Kim Sept. 12, 2022, 5:53 a.m. UTC

Hello,

I found that call stack from the lock tracepoint (using bpf_get_stackid)
can be different on each configuration.  For example it's very different
when I run it on a VM than on a real machine.

v2 changes)
 * rebased to the latest acme/perf/core
 * added a simplified callchain copy

The perf lock contention relies on the stack trace to get the lock
caller names, this kind of difference can be annoying.  Ideally we could
skip stack trace entries for internal BPF or lock functions and get the
correct caller, but it's not the case as of today.  Currently it's hard
coded to control the behavior of stack traces for the lock contention
tracepoints.

To handle those differences, add two new options to control the number of
stack entries and how many it skips.  The default value worked well on
my VM setup, but I had to use --stack-skip=5 on real machines.

You can get it from 'perf/lock-stack-v2' branch in

  git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git

Thanks,
Namhyung


Namhyung Kim (4):
  perf lock contention: Factor out get_symbol_name_offset()
  perf lock contention: Show full callstack with -v option
  perf lock contention: Allow to change stack depth and skip
  perf lock contention: Skip stack trace from BPF

 tools/perf/Documentation/perf-lock.txt        |  6 ++
 tools/perf/builtin-lock.c                     | 97 +++++++++++++++----
 tools/perf/util/bpf_lock_contention.c         | 21 +++-
 .../perf/util/bpf_skel/lock_contention.bpf.c  |  3 +-
 tools/perf/util/lock-contention.h             |  3 +
 5 files changed, 107 insertions(+), 23 deletions(-)


base-commit: 62e64c9d2fd12839c02f1b3e8b873e7cb34e8720