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Subject[PATCH 2/3] tracing/perf: reimplement TP_perf_assign() logic
The next patch tries to avoid the costly perf_trace_buf_* calls
when possible but there is a problem. We can only do this if
__task == NULL, perf_tp_event(task != NULL) has the additional
code for this case.

Unfortunately, TP_perf_assign/__perf_xxx which changes the default
values of __count/__task variables for perf_trace_buf_submit() is
called "too late", after we already did perf_trace_buf_prepare(),
and the optimization above can't work.

So this patch simply embeds __perf_xxx() into TP_ARGS(), this way
DECLARE_EVENT_CLASS() can use the result of assignments hidden in
"args" right after ftrace_get_offsets_##call() which is mostly
trivial. This allows us to have the fast-path "__task != NULL"
check at the start, see the next patch.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
include/trace/events/sched.h | 16 +++-------------
include/trace/ftrace.h | 19 +++++++++++--------
2 files changed, 14 insertions(+), 21 deletions(-)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 249c024..2e7d994 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -57,7 +57,7 @@ DECLARE_EVENT_CLASS(sched_wakeup_template,

TP_PROTO(struct task_struct *p, int success),

- TP_ARGS(p, success),
+ TP_ARGS(__perf_task(p), success),

TP_STRUCT__entry(
__array( char, comm, TASK_COMM_LEN )
@@ -73,9 +73,6 @@ DECLARE_EVENT_CLASS(sched_wakeup_template,
__entry->prio = p->prio;
__entry->success = success;
__entry->target_cpu = task_cpu(p);
- )
- TP_perf_assign(
- __perf_task(p);
),

TP_printk("comm=%s pid=%d prio=%d success=%d target_cpu=%03d",
@@ -313,7 +310,7 @@ DECLARE_EVENT_CLASS(sched_stat_template,

TP_PROTO(struct task_struct *tsk, u64 delay),

- TP_ARGS(tsk, delay),
+ TP_ARGS(__perf_task(tsk), __perf_count(delay)),

TP_STRUCT__entry(
__array( char, comm, TASK_COMM_LEN )
@@ -325,10 +322,6 @@ DECLARE_EVENT_CLASS(sched_stat_template,
memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN);
__entry->pid = tsk->pid;
__entry->delay = delay;
- )
- TP_perf_assign(
- __perf_count(delay);
- __perf_task(tsk);
),

TP_printk("comm=%s pid=%d delay=%Lu [ns]",
@@ -376,7 +369,7 @@ DECLARE_EVENT_CLASS(sched_stat_runtime,

TP_PROTO(struct task_struct *tsk, u64 runtime, u64 vruntime),

- TP_ARGS(tsk, runtime, vruntime),
+ TP_ARGS(tsk, __perf_count(runtime), vruntime),

TP_STRUCT__entry(
__array( char, comm, TASK_COMM_LEN )
@@ -390,9 +383,6 @@ DECLARE_EVENT_CLASS(sched_stat_runtime,
__entry->pid = tsk->pid;
__entry->runtime = runtime;
__entry->vruntime = vruntime;
- )
- TP_perf_assign(
- __perf_count(runtime);
),

TP_printk("comm=%s pid=%d runtime=%Lu [ns] vruntime=%Lu [ns]",
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index aed594a..8886877 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -503,8 +503,14 @@ static inline notrace int ftrace_get_offsets_##call( \
#undef TP_fast_assign
#define TP_fast_assign(args...) args

-#undef TP_perf_assign
-#define TP_perf_assign(args...)
+#undef __perf_addr
+#define __perf_addr(a) (a)
+
+#undef __perf_count
+#define __perf_count(c) (c)
+
+#undef __perf_task
+#define __perf_task(t) (t)

#undef DECLARE_EVENT_CLASS
#define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \
@@ -632,16 +638,13 @@ __attribute__((section("_ftrace_events"))) *__event_##call = &event_##call
#define __get_str(field) (char *)__get_dynamic_array(field)

#undef __perf_addr
-#define __perf_addr(a) __addr = (a)
+#define __perf_addr(a) (__addr = (a))

#undef __perf_count
-#define __perf_count(c) __count = (c)
+#define __perf_count(c) (__count = (c))

#undef __perf_task
-#define __perf_task(t) __task = (t)
-
-#undef TP_perf_assign
-#define TP_perf_assign(args...) args
+#define __perf_task(t) (__task = (t))

#undef DECLARE_EVENT_CLASS
#define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \
--
1.5.5.1


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