From: Steven Rostedt <rostedt@xxxxxxxxxxx>
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))
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
Cc: Clark Willaims <williams@xxxxxxxxxx>
Cc: John Kacur <jkacur@xxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
---
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 8268bf747d6f..c60fd1037b91 100644
--- a/include/trace/trace_events.h
+++ b/include/trace/trace_events.h
@@ -33,6 +33,21 @@
static const char TRACE_SYSTEM_STRING[] = \
__stringify(TRACE_SYSTEM)
+#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; \
+ (u32) do_div(____val, NSEC_PER_SEC); \
+ })
+
TRACE_MAKE_SYSTEM_STR();
#undef TRACE_DEFINE_ENUM
@@ -736,6 +751,16 @@ static inline void ftrace_test_probe_##call(void) \
#undef __print_array
#undef __print_hex_dump
+/*
+ * 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)
--
2.30.2
