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tracing/perf: Reimplement TP_perf_assign() logic

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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.

Link: http://lkml.kernel.org/r/20130806160844.GA2739@redhat.com

Tested-by: David Ahern <dsahern@gmail.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Oleg Nesterov
2013-08-06 18:08:44 +02:00
committed by Steven Rostedt
parent 36009d07b7
commit 12473965c3
2 changed files with 14 additions and 21 deletions
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19
include/trace/ftrace.h
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@@ -507,8 +507,14 @@ 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) \
@@ -636,16 +642,13 @@ __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) \