This is the 5th attempt to fix the report task state issue in sched tracepint, you can check out previous discussions here: v1: https://lore.kernel.org/linux-trace-kernel/20230725072254.32045-1-zegao@xxxxxxxxxxx v2: https://lore.kernel.org/linux-trace-kernel/20230726121618.19198-1-zegao@xxxxxxxxxxx v3: https://lore.kernel.org/linux-trace-kernel/20230801090124.8050-1-zegao@xxxxxxxxxxx v4: sorry for my stupid copy-paste, which makes patch broken and cannot be applied Against v3, reorganize commits so that they can be cherry-picked individually if people indeed have strong opinion over this change. Note PATCH 1-4 are the normal fixes and cleanup whereas PATCH 5-7 introduce new changes. -- FYI, this series are designed not to break anything now and still do the 1-1 correspondence int-char mapping for each distinct task state we want to report, and thus will not lose any details intended for debug purposes. Of course, this might be compromised because of bugs introduced due to my stupidity. So your sage comments are very important and appreciated! -- In the status quo, we should see three different outcomes of the reported sched-out task state from perf-script, perf-sched-timehist, and Tp_printk of tracepoint sched_switch. And it's not hard to figure out that the former two are built upon the third one, and the reason why we see this inconsistency is that the former two does not catch up with the internal change of reported task state definitions as the kernel evolves. IMHO, exporting internal representations of task state in the tracepoint sched_switch is not a good practice and not encouraged at all, which can easily break userspace tools that relies on it. Especially when tracepoints are massively used in many observability tools nowadays due to its stable nature, which makes them no longer used for debug only purpose and we should be careful to decide what ought to be reported to userspace and what ought not. Therefore, to fix the issues mentioned above for good, I proposed to add a new variable to report task state in sched_switch with a symbolic char along with the old hardcoded value, and save the further processing of userspace tools and spare them from knowing implementation details in the kernel. After this patch seires, we report 'RSDTtXZPI' the same as in procfs, plus a 'p' which denotes PREEMP_ACTIVE and is used for sched_switch tracepoint only. Reviews welcome! Regards, Ze -- Ze Gao (5): perf sched: sync state char array with the kernel perf sched: reorganize sched-out task state report code sched, tracing: reorganize fields of switch event struct sched, tracing: add to report task state in symbolic chars perf sched: prefer to use prev_state_char introduced in sched_switch include/trace/events/sched.h | 68 +++++++++++++++++------------- tools/perf/builtin-sched.c | 82 ++++++++++++++++-------------------- 2 files changed, 76 insertions(+), 74 deletions(-) Ze Gao (2): libtraceevent: sync state char array with the kernel libtraceevent: prefer to use prev_state_char introduced in sched_switch plugins/plugin_sched_switch.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) -- 2.41.0
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