perf/trace: Add ability to set a target task for events

A few events are interesting not only for a current task.
For example, sched_stat_* events are interesting for a task
which wakes up. For this reason, it will be good if such
events will be delivered to a target task too.

Now a target task can be set by using __perf_task().

The original idea and a draft patch belongs to Peter Zijlstra.

I need these events for profiling sleep times. sched_switch is used for
getting callchains and sched_stat_* is used for getting time periods.
These events are combined in user space, then it can be analyzed by
perf tools.

Inspired-by: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arun Sharma <asharma@fb.com>
Signed-off-by: Andrew Vagin <avagin@openvz.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1342016098-213063-1-git-send-email-avagin@openvz.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index c6bc2faaf261..a763888a36f9 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -712,6 +712,9 @@ __attribute__((section("_ftrace_events"))) *__event_##call = &event_##call
 #undef __perf_count
 #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
 
@@ -725,6 +728,7 @@ perf_trace_##call(void *__data, proto)					\
         struct ftrace_raw_##call *entry;                                \
         struct pt_regs __regs;                                          \
         u64 __addr = 0, __count = 1;                                    \
+        struct task_struct *__task = NULL;                              \
         struct hlist_head *head;                                        \
         int __entry_size;                                               \
         int __data_size;                                                \
@@ -752,7 +756,7 @@ perf_trace_##call(void *__data, proto)					\
                                                                         \
         head = this_cpu_ptr(event_call->perf_events);                   \
         perf_trace_buf_submit(entry, __entry_size, rctx, __addr,        \
-                __count, &__regs, head);                                \
+                __count, &__regs, head, __task);                        \
 }
 
 /*