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

[Thomas Richter <tmricht@linux.ibm.com>]

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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