From: "Steven Rostedt (Red Hat)" To have nanosecond output displayed in a more human readable format, its nicer to convert it to a seconds format (XXX.YYYYYYYYY). The problem is that to do so, the numbers must be divided by NSEC_PER_SEC, and moded too. But as these numbers are 64 bit, this can not be done simply with '/' and '%' operators, but must use do_div() instead. Instead of performing the expensive do_div() in the hot path of the tracepoint, it is more efficient to perform it during the output phase. But passing in do_div() can confuse the parser, and do_div() doesn't work exactly like a normal C function. It modifies the number in place, and we don't want to modify the actual values in the ring buffer. Two helper functions are now created: __print_ns_to_secs() and __print_ns_without_secs() They both take a value of nanoseconds, and the former will return that number divided by NSEC_PER_SEC, and the latter will mod it with NSEC_PER_SEC giving a way to print a nice human readable format: __print_fmt("time=%llu.%09u", __print_ns_to_secs(REC->nsec_val), __print_ns_without_secs(REC->nsec_val)) Signed-off-by: Steven Rostedt --- include/trace/trace_events.h | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h index 170c93bbdbb7..a1fef8fc352d 100644 --- a/include/trace/trace_events.h +++ b/include/trace/trace_events.h @@ -283,6 +283,21 @@ TRACE_MAKE_SYSTEM_STR(); trace_print_symbols_seq(p, value, symbols); \ }) +#undef __print_ns_to_secs +#define __print_ns_to_secs(value) \ + ({ \ + u64 ____val = (u64)value; \ + do_div(____val, NSEC_PER_SEC); \ + ____val; \ + }) + +#undef __print_ns_without_secs +#define __print_ns_without_secs(value) \ + ({ \ + u64 ____val = (u64)value; \ + do_div(____val, NSEC_PER_SEC); \ + }) + #undef __print_symbolic_u64 #if BITS_PER_LONG == 32 #define __print_symbolic_u64(value, symbol_array...) \ @@ -720,6 +735,16 @@ static inline void ftrace_test_probe_##call(void) \ #undef __get_bitmask #undef __print_array +/* + * The below is not executed in the kernel. It is only what is + * displayed in the print format for userspace to parse. + */ +#undef __print_ns_to_secs +#define __print_ns_to_secs(val) val / 1000000000UL + +#undef __print_ns_without_secs +#define __print_ns_without_secs(val) val % 1000000000UL + #undef TP_printk #define TP_printk(fmt, args...) "\"" fmt "\", " __stringify(args) -- 2.6.4