On Wed, 2013-04-10 at 11:26 +0800, zhangwei(Jovi) wrote:
> From: "zhangwei(Jovi)" <[email protected]>
>
> Currently event tracing only can be use for ftrace and perf,
> there don't have any mechanism to let modules(like external tracing tool)
> register callback tracing function.
>
> Event tracing implement based on tracepoint, compare with raw tracepoint,
> event tracing infrastructure provide built-in structured event annotate
> format,
> this feature should expose to external user.
>
> For example, simple pseudo ktap script demonstrate how to use this event
> tracing expose change.
Ah, it's for ktap.
Lets work on getting ktap into mainline first ;-)
>
> function event_trace(e)
> {
> printf("%s", e.annotate);
> }
>
> os.trace("sched:sched_switch", event_trace);
> os.trace("irq:softirq_raise", event_trace);
>
> The running result:
> sched_switch: prev_comm=rcu_sched prev_pid=10 prev_prio=120 prev_state=S ==>
> next_comm=swapper/1 next_pid=0 next_prio=120
> softirq_raise: vec=1 [action=TIMER]
> ...
>
> This expose change can be use by other tracing tool, like systemtap/lttng,
> if they would implement this.
>
> This patch introduce struct event_trace_ops in trace_array, it have
> two callback functions, pre_trace and do_trace.
> when ftrace_raw_event_<call> function hit, it will call all
> registered event_trace_ops.
>
> the benefit of this change is kernel size shrink ~18K
Now this is something that I would be more interested in having.
>
> (the kernel size will reduce more when perf tracing code
> converting to use this mechanism in future)
>
> text data bss dec hex filename
> 7402131 804364 3149824 11356319 ad489f vmlinux.old
> 7383115 804684 3149824 11337623 acff97 vmlinux.new
>
> Signed-off-by: zhangwei(Jovi) <[email protected]>
> ---
> include/linux/ftrace_event.h | 21 +++++++++++++
> include/linux/trace_array.h | 1 +
> include/trace/ftrace.h | 69
> +++++++++++++-----------------------------
> kernel/trace/trace.c | 4 ++-
> kernel/trace/trace.h | 2 ++
> kernel/trace/trace_events.c | 51 +++++++++++++++++++++++++++++++
> 6 files changed, 99 insertions(+), 49 deletions(-)
>
> diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
> index 4e28b01..4b55272 100644
> --- a/include/linux/ftrace_event.h
> +++ b/include/linux/ftrace_event.h
> @@ -6,6 +6,7 @@
> #include <linux/percpu.h>
> #include <linux/hardirq.h>
> #include <linux/perf_event.h>
> +#include <linux/trace_array.h>
>
> struct trace_array;
> struct trace_buffer;
> @@ -245,6 +246,26 @@ struct ftrace_event_call {
> #endif
> };
>
> +
> +/*
> + * trace_descriptor_t is purpose for passing arguments between
> + * pre_trace and do_trace function.
> + */
> +struct trace_descriptor_t {
> + struct ring_buffer_event *event;
> + struct ring_buffer *buffer;
> + unsigned long irq_flags;
> + int pc;
> +};
> +
> +/* callback function for tracing */
> +struct event_trace_ops {
> + void *(*pre_trace)(struct ftrace_event_file *file,
> + int entry_size, void *data);
> + void (*do_trace)(struct ftrace_event_file *file, void *entry,
> + int entry_size, void *data);
> +};
> +
> struct trace_array;
> struct ftrace_subsystem_dir;
>
> diff --git a/include/linux/trace_array.h b/include/linux/trace_array.h
> index c5b7a13..b362c5f 100644
> --- a/include/linux/trace_array.h
> +++ b/include/linux/trace_array.h
> @@ -56,6 +56,7 @@ struct trace_array {
> struct list_head list;
> char *name;
> struct trace_buffer trace_buffer;
> + struct event_trace_ops *ops;
> #ifdef CONFIG_TRACER_MAX_TRACE
> /*
> * The max_buffer is used to snapshot the trace when a maximum
> diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
> index 4bda044..743e754 100644
> --- a/include/trace/ftrace.h
> +++ b/include/trace/ftrace.h
> @@ -401,41 +401,28 @@ static inline notrace int ftrace_get_offsets_##call(
> \
> *
> * static struct ftrace_event_call event_<call>;
> *
> - * static void ftrace_raw_event_<call>(void *__data, proto)
> + * static notrace void ftrace_raw_event_##call(void *__data, proto)
> * {
> * struct ftrace_event_file *ftrace_file = __data;
> - * struct ftrace_event_call *event_call = ftrace_file->event_call;
> - * struct ftrace_data_offsets_<call> __maybe_unused __data_offsets;
> - * struct ring_buffer_event *event;
> - * struct ftrace_raw_<call> *entry; <-- defined in stage 1
> - * struct ring_buffer *buffer;
> - * unsigned long irq_flags;
> - * int __data_size;
> - * int pc;
> + * struct ftrace_data_offsets_##call __maybe_unused __data_offsets;
> + * struct trace_descriptor_t __desc;
> + * struct event_trace_ops *ops = ftrace_file->tr->ops;
> + * struct ftrace_raw_##call *entry; <-- defined in stage 1
> + * int __data_size, __entry_size;
> *
> - * if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT,
> - * &ftrace_file->flags))
> - * return;
> - *
> - * local_save_flags(irq_flags);
> - * pc = preempt_count();
> - *
> - * __data_size = ftrace_get_offsets_<call>(&__data_offsets, args);
> + * __data_size = ftrace_get_offsets_##call(&__data_offsets, args);
> + * __entry_size = sizeof(*entry) + __data_size;
> *
> - * event = trace_event_buffer_lock_reserve(&buffer, ftrace_file,
> - * event_<call>->event.type,
> - * sizeof(*entry) + __data_size,
> - * irq_flags, pc);
> - * if (!event)
> + * entry = ops->pre_trace(ftrace_file, __entry_size, &__desc);
> + * if (!entry)
> * return;
> - * entry = ring_buffer_event_data(event);
> + *
> + * tstruct
> *
> * { <assign>; } <-- Here we assign the entries by the __field and
> * __array macros.
> *
> - * if (!filter_current_check_discard(buffer, event_call, entry, event))
> - * trace_nowake_buffer_unlock_commit(buffer,
> - * event, irq_flags, pc);
> + * ops->do_trace(ftrace_file, entry, __entry_size, &__desc);
> * }
> *
> * static struct trace_event ftrace_event_type_<call> = {
> @@ -513,38 +500,24 @@ static notrace void
> \
> ftrace_raw_event_##call(void *__data, proto) \
> { \
> struct ftrace_event_file *ftrace_file = __data; \
> - struct ftrace_event_call *event_call = ftrace_file->event_call; \
> struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\
> - struct ring_buffer_event *event; \
> + struct trace_descriptor_t __desc; \
> + struct event_trace_ops *ops = ftrace_file->tr->ops; \
> struct ftrace_raw_##call *entry; \
> - struct ring_buffer *buffer; \
> - unsigned long irq_flags; \
> - int __data_size; \
> - int pc; \
> + int __data_size, __entry_size; \
> \
> - if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, \
> - &ftrace_file->flags)) \
> - return; \
> - \
> - local_save_flags(irq_flags); \
> - pc = preempt_count(); \
> + __data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
> + __entry_size = sizeof(*entry) + __data_size; \
> \
> - __data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
> - \
> - event = trace_event_buffer_lock_reserve(&buffer, ftrace_file, \
> - event_call->event.type, \
> - sizeof(*entry) + __data_size, \
> - irq_flags, pc); \
> - if (!event) \
> + entry = ops->pre_trace(ftrace_file, __entry_size, &__desc); \
> + if (!entry) \
> return; \
> - entry = ring_buffer_event_data(event); \
> \
> tstruct \
> \
> { assign; } \
> \
> - if (!filter_current_check_discard(buffer, event_call, entry, event)) \
> - trace_buffer_unlock_commit(buffer, event, irq_flags, pc); \
> + ops->do_trace(ftrace_file, entry, __entry_size, &__desc); \
> }
Hmm, this is a major change. Something that will definitely have to wait
for 3.12.
-- Steve
> /*
> * The ftrace_test_probe is compiled out, it is only here as a build time
> check
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 829b2be..224b152 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -189,7 +189,7 @@ unsigned long long ns2usecs(cycle_t nsec)
> * pages for the buffer for that CPU. Each CPU has the same number
> * of pages allocated for its buffer.
> */
> -static struct trace_array global_trace;
> +static struct trace_array global_trace = {.ops = &ftrace_events_ops};
>
> LIST_HEAD(ftrace_trace_arrays);
>
> @@ -5773,6 +5773,8 @@ static int new_instance_create(const char *name)
>
> list_add(&tr->list, &ftrace_trace_arrays);
>
> + tr->ops = &ftrace_events_ops;
> +
> mutex_unlock(&trace_types_lock);
>
> return 0;
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index a8acfcd..0a1f4be 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -493,6 +493,8 @@ extern unsigned long nsecs_to_usecs(unsigned long nsecs);
>
> extern unsigned long tracing_thresh;
>
> +extern struct event_trace_ops ftrace_events_ops;
> +
> #ifdef CONFIG_TRACER_MAX_TRACE
> extern unsigned long tracing_max_latency;
>
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 53582e9..09ca479 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -241,6 +241,57 @@ void trace_event_enable_cmd_record(bool enable)
> mutex_unlock(&event_mutex);
> }
>
> +static void *ftrace_events_pre_trace(struct ftrace_event_file *file,
> + int entry_size, void *data)
> +{
> + struct ftrace_event_call *event_call = file->event_call;
> + struct trace_descriptor_t *desc = data;
> + struct ring_buffer_event *event;
> + struct ring_buffer *buffer;
> + unsigned long irq_flags;
> + int pc;
> +
> + if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &file->flags))
> + return NULL;
> +
> + local_save_flags(irq_flags);
> + pc = preempt_count();
> +
> + event = trace_event_buffer_lock_reserve(&buffer, file,
> + event_call->event.type,
> + entry_size, irq_flags, pc);
> +
> + if (!event)
> + return NULL;
> +
> + desc->event = event;
> + desc->buffer = buffer;
> + desc->irq_flags = irq_flags;
> + desc->pc = pc;
> +
> + return ring_buffer_event_data(event);
> +}
> +
> +static void ftrace_events_do_trace(struct ftrace_event_file *file, void
> *entry,
> + int entry_size, void *data)
> +{
> + struct ftrace_event_call *event_call = file->event_call;
> + struct trace_descriptor_t *desc = data;
> + struct ring_buffer_event *event = desc->event;
> + struct ring_buffer *buffer = desc->buffer;
> + unsigned long irq_flags = desc->irq_flags;
> + int pc = desc->pc;
> +
> + if (!filter_current_check_discard(buffer, event_call, entry, event))
> + trace_buffer_unlock_commit(buffer, event, irq_flags, pc);
> +}
> +
> +struct event_trace_ops ftrace_events_ops = {
> + .pre_trace = ftrace_events_pre_trace,
> + .do_trace = ftrace_events_do_trace,
> +};
> +
> +
> static int __ftrace_event_enable_disable(struct ftrace_event_file *file,
> int enable, int soft_disable)
> {
--
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