Messages in this thread |  | | Subject | Re: [PATCH 7/9] ftrace, perf: Add support to use function tracepoint in perf | | From | Steven Rostedt <> | | Date | Mon, 28 Nov 2011 14:58:38 -0500 |
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On Sun, 2011-11-27 at 19:04 +0100, Jiri Olsa wrote: > Adding perf registration support for the ftrace function event, > so it is now possible to register it via perf interface. > > The perf_event struct statically contains ftrace_ops as a handle > for function tracer. The function tracer is registered/unregistered > in open/close actions, and enabled/disabled in add/del actions. > > It is now possible to use function trace within perf commands > like: > > perf record -e ftrace:function ls > perf stat -e ftrace:function ls
Question. This is a root only command, correct? Otherwise, we are allowing any user to create a large performance impact to the system.
> > Signed-off-by: Jiri Olsa <jolsa@redhat.com> > --- > include/linux/perf_event.h | 3 + > kernel/trace/trace_event_perf.c | 88 +++++++++++++++++++++++++++++++++++++++ > kernel/trace/trace_export.c | 23 ++++++++++ > 3 files changed, 114 insertions(+), 0 deletions(-) > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index 1e9ebe5..6071995 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -847,6 +847,9 @@ struct perf_event { > #ifdef CONFIG_EVENT_TRACING > struct ftrace_event_call *tp_event; > struct event_filter *filter; > +#ifdef CONFIG_FUNCTION_TRACER > + struct ftrace_ops ftrace_ops; > +#endif > #endif > > #ifdef CONFIG_CGROUP_PERF > diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c > index d72af0b..4be0f73 100644 > --- a/kernel/trace/trace_event_perf.c > +++ b/kernel/trace/trace_event_perf.c > @@ -250,3 +250,91 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type, > return raw_data; > } > EXPORT_SYMBOL_GPL(perf_trace_buf_prepare); > + > + > +static void > +perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip) > +{ > + struct ftrace_entry *entry; > + struct hlist_head *head; > + struct pt_regs regs; > + int rctx; > + > +#define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \ > + sizeof(u64)) - sizeof(u32)) > + > + BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE); > + > + perf_fetch_caller_regs(®s); > + > + entry = perf_trace_buf_prepare(ENTRY_SIZE, TRACE_FN, NULL, &rctx); > + if (!entry) > + return; > + > + entry->ip = ip; > + entry->parent_ip = parent_ip; > + > + head = this_cpu_ptr(event_function.perf_events); > + perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0, > + 1, ®s, head); > + > +#undef ENTRY_SIZE > +} > + > +static int perf_ftrace_function_register(struct perf_event *event) > +{ > + struct ftrace_ops *ops = &event->ftrace_ops; > + > + ops->flags |= FTRACE_OPS_FL_CONTROL; > + atomic_set(&ops->disabled, 1); > + ops->func = perf_ftrace_function_call; > + return register_ftrace_function(ops);
When is ADD called? Because as soon as you register this function, even though you have it "disabled" the system takes about a 13% impact on performance just by calling this.
> +} > + > +static int perf_ftrace_function_unregister(struct perf_event *event) > +{ > + struct ftrace_ops *ops = &event->ftrace_ops; > + return unregister_ftrace_function(ops); > +} > + > +static void perf_ftrace_function_enable(struct perf_event *event) > +{ > + struct ftrace_ops *ops = &event->ftrace_ops; > + enable_ftrace_function(ops);
Is it really an issue that we shouldn't call the full blown register instead? I'm not really understanding why this is a problem. Note, one of the improvements to ftrace in the near future is to enable ftrace without stop_machine.
-- Steve
> +} > + > +static void perf_ftrace_function_disable(struct perf_event *event) > +{ > + struct ftrace_ops *ops = &event->ftrace_ops; > + disable_ftrace_function(ops); > +} > + > +int perf_ftrace_event_register(struct ftrace_event_call *call, > + enum trace_reg type, void *data) > +{ > + int etype = call->event.type; > + > + if (etype != TRACE_FN) > + return -EINVAL; > + > + switch (type) { > + case TRACE_REG_REGISTER: > + case TRACE_REG_UNREGISTER: > + break; > + case TRACE_REG_PERF_REGISTER: > + case TRACE_REG_PERF_UNREGISTER: > + return 0; > + case TRACE_REG_PERF_OPEN: > + return perf_ftrace_function_register(data); > + case TRACE_REG_PERF_CLOSE: > + return perf_ftrace_function_unregister(data); > + case TRACE_REG_PERF_ADD: > + perf_ftrace_function_enable(data); > + return 0; > + case TRACE_REG_PERF_DEL: > + perf_ftrace_function_disable(data); > + return 0; > + } > + > + return -EINVAL; > +} > diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c > index bbeec31..62e86a5 100644 > --- a/kernel/trace/trace_export.c > +++ b/kernel/trace/trace_export.c > @@ -131,6 +131,28 @@ ftrace_define_fields_##name(struct ftrace_event_call *event_call) \ > > #include "trace_entries.h" > > +static int ftrace_event_class_register(struct ftrace_event_call *call, > + enum trace_reg type, void *data) > +{ > + switch (type) { > + case TRACE_REG_PERF_REGISTER: > + case TRACE_REG_PERF_UNREGISTER: > + return 0; > + case TRACE_REG_PERF_OPEN: > + case TRACE_REG_PERF_CLOSE: > + case TRACE_REG_PERF_ADD: > + case TRACE_REG_PERF_DEL: > +#ifdef CONFIG_PERF_EVENTS > + return perf_ftrace_event_register(call, type, data); > +#endif > + case TRACE_REG_REGISTER: > + case TRACE_REG_UNREGISTER: > + break; > + } > + > + return -EINVAL; > +} > + > #undef __entry > #define __entry REC > > @@ -159,6 +181,7 @@ struct ftrace_event_class event_class_ftrace_##call = { \ > .system = __stringify(TRACE_SYSTEM), \ > .define_fields = ftrace_define_fields_##call, \ > .fields = LIST_HEAD_INIT(event_class_ftrace_##call.fields),\ > + .reg = ftrace_event_class_register, \ > }; \ > \ > struct ftrace_event_call __used event_##call = { \
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