Re: [PATCH v6 0/5] perf evsel fallback changes, better s390 defaults

Thomas Richter
2026-03-18T08:20:53Z

On 3/17/26 18:56, Ian Rogers wrote:
> Discussion with Thomas Richter in:
> https://lore.kernel.org/lkml/20260306071002.2526085-1-tmricht@linux.ibm.com/
> showed that the evsel__fallback wasn't working for s390. These patches
> avoid the problematic frame pointer callchain on s390 and fix
> evsel__fallback from a range of problems when falling back to a
> software event. I simulated failures when developing the patches but
> they are untested other than that.
>
> v6: Sashiko noted that target wasn't fully set up when creating the
> default evlist in `perf top`, so move it earlier. Fix const char*
> casting issues in __parse_callchain_report_opt. Make '-g' not
> override the .perfconfig setting again.
> https://sashiko.dev/#/patchset/20260317055334.760347-1-irogers%40google.com
>
> v5: Fix the value for the top option to match that of record. Tidy the
> callchain parsing option callbacks. Based on AI review feedback:
> https://sashiko.dev/#/patchset/20260317030601.567422-1-irogers%40google.com
> https://lore.kernel.org/lkml/20260317055334.760347-1-irogers@google.com/
>
> v4: Changing the callchain parameter at configuration time means other
> options aren't set the same as they would for `--call-graph
> dwarf`, for example the stack size. Switch to setting the
> callchain option on s390 to parameter parse time. For '-g' use
> '--call-graph dwarf' for s390. Other --call-graph options are
> parsed as normal, but a warning is generated when setting
> `--call-graph fp` for s390. Also fix that sample IDs aren't wanted
> when there is only 1 event in the evlist.
> https://lore.kernel.org/lkml/20260317030601.567422-1-irogers@google.com/
>
> v3: Incorporate feedback about event and callchain behavior for s390:
> https://lore.kernel.org/lkml/20260312061628.1593105-1-irogers@google.com/
> https://lore.kernel.org/lkml/20260313202811.2599195-1-irogers@google.com/
>
> v2: try exclude_callchain_user for s390 rather than fully disabling
> the callchain. Fix a missed clearing of is_pmu_core if the
> software event fallback.
> https://lore.kernel.org/lkml/20260312061628.1593105-1-irogers@google.com/
>
> v1: https://lore.kernel.org/lkml/20260312031928.1494864-1-irogers@google.com/
>
> Ian Rogers (5):
> perf evsel: Improve falling back from cycles
> perf target: Constify simple check functions
> perf evsel: Constify option arguments to config functions
> perf callchain: Refactor callchain option parsing
> perf evlist: Improve default event for s390
>
> tools/perf/builtin-record.c | 66 +++++++----------------------
> tools/perf/builtin-top.c | 67 ++++++++++++++++-------------
> tools/perf/builtin-trace.c | 9 +++-
> tools/perf/tests/event_update.c | 4 +-
> tools/perf/tests/expand-cgroup.c | 4 +-
> tools/perf/tests/perf-record.c | 7 ++-
> tools/perf/tests/topology.c | 4 +-
> tools/perf/util/callchain.c | 73 ++++++++++++++++++++++++++------
> tools/perf/util/callchain.h | 12 ++----
> tools/perf/util/evlist.c | 32 +++++++++-----
> tools/perf/util/evlist.h | 2 +-
> tools/perf/util/evsel.c | 70 +++++++++++++++++++-----------
> tools/perf/util/evsel.h | 10 +++--
> tools/perf/util/target.h | 12 +++---
> 14 files changed, 217 insertions(+), 155 deletions(-)
>

Ian, thanks a lot. I tested it using the same sequences as for v5.

Tested-by: Thomas Richter <tmricht@linux.ibm.com>

--
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
IBM Deutschland Research & Development GmbH

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