On Fri, Oct 04, 2013 at 10:53:42AM -0400, Steven Rostedt wrote: > In other words, what does these flags in the trace actually mean? > Probably need to add comments in the code and/or update the > Documentation section If "task need resched" is supposed to explain things; the below too will suffice... muwhahaha! --- Subject: ftrace, sched: Add TRACE_FLAG_PREEMPT_RESCHED From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Date: Fri Sep 27 17:11:00 CEST 2013 Since the introduction of PREEMPT_NEED_RESCHED; see commit: f27dde8deef3 ("sched: Add NEED_RESCHED to the preempt_count") we need to be able to look at both TIF_NEED_RESCHED and PREEMPT_NEED_RESCHED to understand the full preemption behaviour. Add it to the trace output. Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/n/tip-1tys5rfpbpi7ky20b7msh4qy@xxxxxxxxxxxxxx --- Documentation/trace/ftrace.txt | 6 +++++- kernel/trace/trace.c | 3 ++- kernel/trace/trace.h | 1 + kernel/trace/trace_output.c | 13 +++++++++++-- 4 files changed, 19 insertions(+), 4 deletions(-) --- a/Documentation/trace/ftrace.txt +++ b/Documentation/trace/ftrace.txt @@ -655,7 +655,11 @@ explains which is which. read the irq flags variable, an 'X' will always be printed here. - need-resched: 'N' task need_resched is set, '.' otherwise. + need-resched: + 'N' both TIF_NEED_RESCHED and PREEMPT_NEED_RESCHED is set, + 'n' only TIF_NEED_RESCHED is set, + 'p' only PREEMPT_NEED_RESCHED is set, + '.' otherwise. hardirq/softirq: 'H' - hard irq occurred inside a softirq. --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1509,7 +1509,8 @@ tracing_generic_entry_update(struct trac #endif ((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) | ((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) | - (need_resched() ? TRACE_FLAG_NEED_RESCHED : 0); + (tif_need_resched() ? TRACE_FLAG_NEED_RESCHED : 0) | + (test_preempt_need_resched() ? TRACE_FLAG_PREEMPT_RESCHED : 0); } EXPORT_SYMBOL_GPL(tracing_generic_entry_update); --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -124,6 +124,7 @@ enum trace_flag_type { TRACE_FLAG_NEED_RESCHED = 0x04, TRACE_FLAG_HARDIRQ = 0x08, TRACE_FLAG_SOFTIRQ = 0x10, + TRACE_FLAG_PREEMPT_RESCHED = 0x20, }; #define TRACE_BUF_SIZE 1024 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -618,8 +618,17 @@ int trace_print_lat_fmt(struct trace_seq (entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' : (entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ? 'X' : '.'; - need_resched = - (entry->flags & TRACE_FLAG_NEED_RESCHED) ? 'N' : '.'; + + if ((entry->flags & TRACE_FLAG_NEED_RESCHED) && + (entry->flags & TRACE_FLAG_PREEMPT_RESCHED)) + need_resched = 'N'; + else if (entry->flags & TRACE_FLAG_NEED_RESCHED) + need_resched = 'n'; + else if (entry->flags & TRACE_FLAG_PREEMPT_RESCHED) + need_resched = 'p'; + else + need_resched = '.'; + hardsoft_irq = (hardirq && softirq) ? 'H' : hardirq ? 'h' : -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html