This is the 3rd 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 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! diff from v2: 1. reorder to condense sched_switch record structure 2. fallback to older method to maintain backward compatibility for perf/libtraceevent 3. split housekeeping work into separate ones for readability -- 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: add to report task state in symbolic chars sched, tracing: reorganize fields of switch event struct 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 (1): libtraceevent: prefer to use prev_state_char introduced in sched_switch plugins/plugin_sched_switch.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) -- 2.40.1
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