| Message ID | 4CBDA7B1.6020902@siemens.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Oct 19, 2010 at 04:14:09PM +0200, Jan Kiszka wrote: > Instead of preparing all traced args, jumping into the common trace > function, even collecting a timestamp, do the check if a particular > tracepoint is enabled inline. Also, mark the enabled case unlikely to > motivate the compiler to push the trace code out of the fastpath. > > Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> > --- > simpletrace.c | 4 ---- > tracetool | 7 +++++-- > 2 files changed, 5 insertions(+), 6 deletions(-) Acked-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
diff --git a/simpletrace.c b/simpletrace.c index deb1e07..224e4ab 100644 --- a/simpletrace.c +++ b/simpletrace.c @@ -148,10 +148,6 @@ static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, */ clock_gettime(CLOCK_MONOTONIC, &ts); - if (!trace_list[event].state) { - return; - } - rec->event = event; rec->timestamp_ns = ts.tv_sec * 1000000000LL + ts.tv_nsec; rec->x1 = x1; diff --git a/tracetool b/tracetool index 7010858..9532409 100755 --- a/tracetool +++ b/tracetool @@ -146,6 +146,8 @@ linetoh_begin_simple() { cat <<EOF #include "simpletrace.h" + +extern TraceEvent trace_list[]; EOF simple_event_num=0 @@ -179,7 +181,9 @@ linetoh_simple() cat <<EOF static inline void trace_$name($args) { - trace$argc($trace_args); + if (unlikely(trace_list[$simple_event_num].state)) { + trace$argc($trace_args); + } } EOF @@ -190,7 +194,6 @@ linetoh_end_simple() { cat <<EOF #define NR_TRACE_EVENTS $simple_event_num -extern TraceEvent trace_list[NR_TRACE_EVENTS]; EOF }
Instead of preparing all traced args, jumping into the common trace function, even collecting a timestamp, do the check if a particular tracepoint is enabled inline. Also, mark the enabled case unlikely to motivate the compiler to push the trace code out of the fastpath. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> --- simpletrace.c | 4 ---- tracetool | 7 +++++-- 2 files changed, 5 insertions(+), 6 deletions(-)