Hi Byungchul, On Mon, 17 Nov 2014 09:41:57 +0900, byungchul park wrote: > From: Byungchul Park <byungchul.p...@lge.com> > > Currently, function graph tracer prints "!" or "+" just before > function execution time to signal a function overhead, depending > on the time. Even it is usually enough to do that, we sometimes > need to be signaled for bigger execution time than 100 micro seconds. > > For example, I used function graph tracer to detect if there is > any case that exit_mm() takes too much time. I did following steps > in /sys/kernel/debug/tracing. It was easier to detect very big > excution time with patched kernel than with original kernel. > > $ echo exit_mm > set_graph_function > $ echo function_graph > current_tracer > $ echo > trace > $ cat trace_pipe > $LOGFILE > ... (do something and terminate logging) > $ grep "\\$" $LOGFILE > 3) $ 22082032 us | } /* kernel_map_pages */ > 3) $ 22082040 us | } /* free_pages_prepare */ > 3) $ 22082113 us | } /* free_hot_cold_page */ > 3) $ 22083455 us | } /* free_hot_cold_page_list */ > 3) $ 22083895 us | } /* release_pages */ > 3) $ 22177873 us | } /* free_pages_and_swap_cache */ > 3) $ 22178929 us | } /* unmap_single_vma */ > 3) $ 22198885 us | } /* unmap_vmas */ > 3) $ 22206949 us | } /* exit_mmap */ > 3) $ 22207659 us | } /* mmput */ > 3) $ 22207793 us | } /* exit_mm */ > > And then, it was easy to find out that a schedule-out occured by > sub_preempt_count() within kernel_map_pages(). > > To detect very large function exection time caused by either problematic > function implementation or scheduling issues, this patch can be useful. > > Signed-off-by: Byungchul Park <byungchul.p...@lge.com> > --- > Documentation/trace/ftrace.txt | 2 ++ > kernel/trace/trace.h | 19 +++++++++++++++++++ > kernel/trace/trace_functions_graph.c | 20 ++++++++++++++------ > 3 files changed, 35 insertions(+), 6 deletions(-) > > diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt > index 4da4261..f827e2f 100644 > --- a/Documentation/trace/ftrace.txt > +++ b/Documentation/trace/ftrace.txt > @@ -1951,6 +1951,8 @@ want, depending on your needs. > > + means that the function exceeded 10 usecs. > ! means that the function exceeded 100 usecs. > + # means that the function exceeded 1000 usecs. > + $ means that the function exceeded 1 sec. > > > - The task/pid field displays the thread cmdline and pid which > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h > index 385391f..d89868a 100644 > --- a/kernel/trace/trace.h > +++ b/kernel/trace/trace.h > @@ -331,6 +331,25 @@ struct tracer_flags { > /* Makes more easy to define a tracer opt */ > #define TRACER_OPT(s, b) .name = #s, .bit = b > > +/* trace overhead mark */ > +struct trace_mark { > + unsigned long long val; /* unit: nsec */ > + char sym; > +}; > + > +#define MARK(v, s) {.val = v, .sym = s} > + > +static inline char trace_duration_mark(unsigned long long d, > + const struct trace_mark m[], > + int size) > +{ > + int idx = size; > + > + if (size <= 0) return ' '; > + while (d <= m[--idx].val && idx > 0); > + > + return m[idx].sym; > +}
I think it'd be simpler if you arrange the mark array in an opposity order: static const struct trace_mark mark[] = { MARK(1000000000ULL , '$'), /* 1 sec */ MARK(1000000ULL , '#'), /* 1000 usecs */ MARK(100000ULL , '!'), /* 100 usecs */ MARK(10000ULL , '+'), /* 10 usecs */ MARK(0ULL , ' '), /* 0 usecs */ }; static inline char trace_duration_mark(unsigned long long d, const struct trace_mark m[], int size) { int i; for (i = 0; i < size; i++) { if (d >= m[i].val) break; } return m[i].sym; } Thanks, Namhyung > > /** > * struct tracer - a specific tracer and its callbacks to interact with > debugfs > diff --git a/kernel/trace/trace_functions_graph.c > b/kernel/trace/trace_functions_graph.c > index cb33f46..d9ac09f 100644 > --- a/kernel/trace/trace_functions_graph.c > +++ b/kernel/trace/trace_functions_graph.c > @@ -797,6 +797,19 @@ trace_print_graph_duration(unsigned long long duration, > struct trace_seq *s) > return TRACE_TYPE_HANDLED; > } > > +static const struct trace_mark mark[] = { > + MARK(0ULL , ' '), /* 0 usecs */ > + MARK(10000ULL , '+'), /* 10 usecs */ > + MARK(100000ULL , '!'), /* 100 usecs */ > + MARK(1000000ULL , '#'), /* 1000 usecs */ > + MARK(1000000000ULL , '$'), /* 1 sec */ > +}; > + > +static inline char find_trace_mark(unsigned long long d) > +{ > + return trace_duration_mark(d, mark, ARRAY_SIZE(mark)); > +} > + > static enum print_line_t > print_graph_duration(unsigned long long duration, struct trace_seq *s, > u32 flags) > @@ -822,12 +835,7 @@ print_graph_duration(unsigned long long duration, struct > trace_seq *s, > > /* Signal a overhead of time execution to the output */ > if (flags & TRACE_GRAPH_PRINT_OVERHEAD) { > - /* Duration exceeded 100 usecs */ > - if (duration > 100000ULL) > - ret = trace_seq_puts(s, "! "); > - /* Duration exceeded 10 usecs */ > - else if (duration > 10000ULL) > - ret = trace_seq_puts(s, "+ "); > + ret = trace_seq_printf(s, "%c ", find_trace_mark(duration)); > } > > /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/