From: Steven Rostedt Impact: lower overhead tracing The current event tracer can automatically pick up trace points that are registered with the TRACE_FORMAT macro. But it required a printf format string and parsing. Although, this adds the ability to get guaranteed information like task names and such, it took a hit in overhead processing. This processing can add about 500-1000 nanoseconds overhead, but in some cases that too is considered too much and we want to shave off as much from this overhead as possible. Tom Zanussi recently posted tracing patches to lkml that are based on a nice idea about capturing the data via C structs using STRUCT_ENTER, STRUCT_EXIT type of macros. I liked that method very much, but did not like the implementation that required a developer to add data/code in several disjoint locations. This patch extends the event_tracer macros to do a similar "raw C" approach that Tom Zanussi did. But instead of having the developers needing to tweak a bunch of code all over the place, they can do it all in one macro - preferably placed near the code that it is tracing. That makes it much more likely that tracepoints will be maintained on an ongoing basis by the code they modify. The new macro TRACE_EVENT_FORMAT is created for this approach. (Note, a developer may still utilize the more low level DECLARE_TRACE macros if they don't care about getting their traces automatically in the event tracer.) They can also use the existing TRACE_FORMAT if they don't need to code the tracepoint in C, but just want to use the convenience of printf. So if the developer wants to "hardwire" a tracepoint in the fastest possible way, and wants to acquire their data via a user space utility in a raw binary format, or wants to see it in the trace output but not sacrifice any performance, then they can implement the faster but more complex TRACE_EVENT_FORMAT macro. Here's what usage looks like: TRACE_EVENT_FORMAT(name, TPPROTO(proto), TPARGS(args), TPFMT(fmt, fmt_args), TRACE_STUCT( TRACE_FIELD(type1, item1, assign1) TRACE_FIELD(type2, item2, assign2) [...] ), TPRAWFMT(raw_fmt) ); Note name, proto, args, and fmt, are all identical to what TRACE_FORMAT uses. name: is the unique identifier of the trace point proto: The proto type that the trace point uses args: the args in the proto type fmt: printf format to use with the event printf tracer fmt_args: the printf argments to match fmt TRACE_STRUCT starts the ability to create a structure. Each item in the structure is defined with a TRACE_FIELD TRACE_FIELD(type, item, assign) type: the C type of item. item: the name of the item in the stucture assign: what to assign the item in the trace point callback raw_fmt is a way to pretty print the struct. It must match the order of the items are added in TRACE_STUCT An example of this would be: TRACE_EVENT_FORMAT(sched_wakeup, TPPROTO(struct rq *rq, struct task_struct *p, int success), TPARGS(rq, p, success), TPFMT("task %s:%d %s", p->comm, p->pid, success?"succeeded":"failed"), TRACE_STRUCT( TRACE_FIELD(pid_t, pid, p->pid) TRACE_FIELD(int, success, success) ), TPRAWFMT("task %d success=%d") ); This creates us a unique struct of: struct { pid_t pid; int success; }; And the way the call back would assign these values would be: entry->pid = p->pid; entry->success = success; The nice part about this is that the creation of the assignent is done via macro magic in the event tracer. Once the TRACE_EVENT_FORMAT is created, the developer will then have a faster method to record into the ring buffer. They do not need to worry about the tracer itself. The developer would only need to touch the files in include/trace/*.h Again, I would like to give special thanks to Tom Zanussi for this nice idea. Idea-from: Tom Zanussi Signed-off-by: Steven Rostedt --- kernel/trace/events.c | 6 +- kernel/trace/trace.h | 19 +++ kernel/trace/trace_events.c | 2 +- kernel/trace/trace_events.h | 57 --------- kernel/trace/trace_events_stage_1.h | 34 ++++++ kernel/trace/trace_events_stage_2.h | 72 ++++++++++++ kernel/trace/trace_events_stage_3.h | 219 +++++++++++++++++++++++++++++++++++ 7 files changed, 350 insertions(+), 59 deletions(-) delete mode 100644 kernel/trace/trace_events.h create mode 100644 kernel/trace/trace_events_stage_1.h create mode 100644 kernel/trace/trace_events_stage_2.h create mode 100644 kernel/trace/trace_events_stage_3.h diff --git a/kernel/trace/events.c b/kernel/trace/events.c index 4e4e458..f2509cb 100644 --- a/kernel/trace/events.c +++ b/kernel/trace/events.c @@ -8,6 +8,10 @@ #include -#include "trace_events.h" +#include "trace_output.h" + +#include "trace_events_stage_1.h" +#include "trace_events_stage_2.h" +#include "trace_events_stage_3.h" #include diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index adf161f..aa1ab0c 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -726,4 +726,23 @@ static inline void trace_branch_disable(void) } #endif /* CONFIG_BRANCH_TRACER */ +struct ftrace_event_call { + char *name; + char *system; + struct dentry *dir; + int enabled; + int (*regfunc)(void); + void (*unregfunc)(void); + int id; + struct dentry *raw_dir; + int raw_enabled; + int (*raw_init)(void); + int (*raw_reg)(void); + void (*raw_unreg)(void); +}; + +void event_trace_printk(unsigned long ip, const char *fmt, ...); +extern struct ftrace_event_call __start_ftrace_events[]; +extern struct ftrace_event_call __stop_ftrace_events[]; + #endif /* _LINUX_KERNEL_TRACE_H */ diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index b811eb3..77a5c02 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -10,7 +10,7 @@ #include #include -#include "trace_events.h" +#include "trace.h" #define TRACE_SYSTEM "TRACE_SYSTEM" diff --git a/kernel/trace/trace_events.h b/kernel/trace/trace_events.h deleted file mode 100644 index b015d7b..0000000 --- a/kernel/trace/trace_events.h +++ /dev/null @@ -1,57 +0,0 @@ -#ifndef _LINUX_KERNEL_TRACE_EVENTS_H -#define _LINUX_KERNEL_TRACE_EVENTS_H - -#include -#include -#include "trace.h" - -struct ftrace_event_call { - char *name; - char *system; - struct dentry *dir; - int enabled; - int (*regfunc)(void); - void (*unregfunc)(void); -}; - - -#undef TPFMT -#define TPFMT(fmt, args...) fmt "\n", ##args - -#undef TRACE_FORMAT -#define TRACE_FORMAT(call, proto, args, fmt) \ -static void ftrace_event_##call(proto) \ -{ \ - event_trace_printk(_RET_IP_, "(" #call ") " fmt); \ -} \ - \ -static int ftrace_reg_event_##call(void) \ -{ \ - int ret; \ - \ - ret = register_trace_##call(ftrace_event_##call); \ - if (!ret) \ - pr_info("event trace: Could not activate trace point " \ - "probe to " #call); \ - return ret; \ -} \ - \ -static void ftrace_unreg_event_##call(void) \ -{ \ - unregister_trace_##call(ftrace_event_##call); \ -} \ - \ -static struct ftrace_event_call __used \ -__attribute__((__aligned__(4))) \ -__attribute__((section("_ftrace_events"))) event_##call = { \ - .name = #call, \ - .system = STR(TRACE_SYSTEM), \ - .regfunc = ftrace_reg_event_##call, \ - .unregfunc = ftrace_unreg_event_##call, \ -} - -void event_trace_printk(unsigned long ip, const char *fmt, ...); -extern struct ftrace_event_call __start_ftrace_events[]; -extern struct ftrace_event_call __stop_ftrace_events[]; - -#endif /* _LINUX_KERNEL_TRACE_EVENTS_H */ diff --git a/kernel/trace/trace_events_stage_1.h b/kernel/trace/trace_events_stage_1.h new file mode 100644 index 0000000..fd3bf93 --- /dev/null +++ b/kernel/trace/trace_events_stage_1.h @@ -0,0 +1,34 @@ +/* + * Stage 1 of the trace events. + * + * Override the macros in to include the following: + * + * struct ftrace_raw_ { + * struct trace_entry ent; + * ; + * [...] + * }; + * + * The is created by the TRACE_FIELD(type, item, assign) + * macro. We simply do "type item;", and that will create the fields + * in the structure. + */ + +#undef TRACE_FORMAT +#define TRACE_FORMAT(call, proto, args, fmt) + +#undef TRACE_EVENT_FORMAT +#define TRACE_EVENT_FORMAT(name, proto, args, fmt, tstruct, tpfmt) \ + struct ftrace_raw_##name { \ + struct trace_entry ent; \ + tstruct \ + }; \ + static struct ftrace_event_call event_##name + +#undef TRACE_STRUCT +#define TRACE_STRUCT(args...) args + +#define TRACE_FIELD(type, item, assign) \ + type item; + +#include diff --git a/kernel/trace/trace_events_stage_2.h b/kernel/trace/trace_events_stage_2.h new file mode 100644 index 0000000..3eaaef5 --- /dev/null +++ b/kernel/trace/trace_events_stage_2.h @@ -0,0 +1,72 @@ +/* + * Stage 2 of the trace events. + * + * Override the macros in to include the following: + * + * enum print_line_t + * ftrace_raw_output_(struct trace_iterator *iter, int flags) + * { + * struct trace_seq *s = &iter->seq; + * struct ftrace_raw_ *field; <-- defined in stage 1 + * struct trace_entry *entry; + * int ret; + * + * entry = iter->ent; + * + * if (entry->type != event_.id) { + * WARN_ON_ONCE(1); + * return TRACE_TYPE_UNHANDLED; + * } + * + * field = (typeof(field))entry; + * + * ret = trace_seq_printf(s, "%s", "\n"); + * if (!ret) + * return TRACE_TYPE_PARTIAL_LINE; + * + * return TRACE_TYPE_HANDLED; + * } + * + * This is the method used to print the raw event to the trace + * output format. Note, this is not needed if the data is read + * in binary. + */ + +#undef TRACE_STRUCT +#define TRACE_STRUCT(args...) args + +#undef TRACE_FIELD +#define TRACE_FIELD(type, item, assign) \ + field->item, + + +#undef TPRAWFMT +#define TPRAWFMT(args...) args + +#undef TRACE_EVENT_FORMAT +#define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt) \ +enum print_line_t \ +ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \ +{ \ + struct trace_seq *s = &iter->seq; \ + struct ftrace_raw_##call *field; \ + struct trace_entry *entry; \ + int ret; \ + \ + entry = iter->ent; \ + \ + if (entry->type != event_##call.id) { \ + WARN_ON_ONCE(1); \ + return TRACE_TYPE_UNHANDLED; \ + } \ + \ + field = (typeof(field))entry; \ + \ + ret = trace_seq_printf(s, tpfmt "%s", tstruct "\n"); \ + if (!ret) \ + return TRACE_TYPE_PARTIAL_LINE; \ + \ + return TRACE_TYPE_HANDLED; \ +} + +#include diff --git a/kernel/trace/trace_events_stage_3.h b/kernel/trace/trace_events_stage_3.h new file mode 100644 index 0000000..7a161c4 --- /dev/null +++ b/kernel/trace/trace_events_stage_3.h @@ -0,0 +1,219 @@ +/* + * Stage 3 of the trace events. + * + * Override the macros in to include the following: + * + * static void ftrace_event_(proto) + * { + * event_trace_printk(_RET_IP_, "() " ); + * } + * + * static int ftrace_reg_event_(void) + * { + * int ret; + * + * ret = register_trace_(ftrace_event_); + * if (!ret) + * pr_info("event trace: Could not activate trace point " + * "probe to "); + * return ret; + * } + * + * static void ftrace_unreg_event_(void) + * { + * unregister_trace_(ftrace_event_); + * } + * + * For those macros defined with TRACE_FORMAT: + * + * static struct ftrace_event_call __used + * __attribute__((__aligned__(4))) + * __attribute__((section("_ftrace_events"))) event_ = { + * .name = "", + * .regfunc = ftrace_reg_event_, + * .unregfunc = ftrace_unreg_event_, + * } + * + * + * For those macros defined with TRACE_EVENT_FORMAT: + * + * static struct ftrace_event_call event_; + * + * static void ftrace_raw_event_(proto) + * { + * struct ring_buffer_event *event; + * struct ftrace_raw_ *entry; <-- defined in stage 1 + * unsigned long irq_flags; + * int pc; + * + * local_save_flags(irq_flags); + * pc = preempt_count(); + * + * event = trace_current_buffer_lock_reserve(event_.id, + * sizeof(struct ftrace_raw_), + * irq_flags, pc); + * if (!event) + * return; + * entry = ring_buffer_event_data(event); + * + * ; <-- Here we assign the entries by the TRACE_FIELD. + * + * trace_current_buffer_unlock_commit(event, irq_flags, pc); + * } + * + * static int ftrace_raw_reg_event_(void) + * { + * int ret; + * + * ret = register_trace_(ftrace_raw_event_); + * if (!ret) + * pr_info("event trace: Could not activate trace point " + * "probe to "); + * return ret; + * } + * + * static void ftrace_unreg_event_(void) + * { + * unregister_trace_(ftrace_raw_event_); + * } + * + * static struct trace_event ftrace_event_type_ = { + * .trace = ftrace_raw_output_, <-- stage 2 + * }; + * + * static int ftrace_raw_init_event_(void) + * { + * int id; + * + * id = register_ftrace_event(&ftrace_event_type_); + * if (!id) + * return -ENODEV; + * event_.id = id; + * return 0; + * } + * + * static struct ftrace_event_call __used + * __attribute__((__aligned__(4))) + * __attribute__((section("_ftrace_events"))) event_ = { + * .name = "", + * .regfunc = ftrace_reg_event_, + * .unregfunc = ftrace_unreg_event_, + * .raw_init = ftrace_raw_init_event_, + * .raw_reg = ftrace_raw_reg_event_, + * .raw_unreg = ftrace_raw_unreg_event_, + * } + * + */ + +#undef TPFMT +#define TPFMT(fmt, args...) fmt "\n", ##args + +#define _TRACE_FORMAT(call, proto, args, fmt) \ +static void ftrace_event_##call(proto) \ +{ \ + event_trace_printk(_RET_IP_, "(" #call ") " fmt); \ +} \ + \ +static int ftrace_reg_event_##call(void) \ +{ \ + int ret; \ + \ + ret = register_trace_##call(ftrace_event_##call); \ + if (!ret) \ + pr_info("event trace: Could not activate trace point " \ + "probe to " #call); \ + return ret; \ +} \ + \ +static void ftrace_unreg_event_##call(void) \ +{ \ + unregister_trace_##call(ftrace_event_##call); \ +} \ + + +#undef TRACE_FORMAT +#define TRACE_FORMAT(call, proto, args, fmt) \ +_TRACE_FORMAT(call, PARAMS(proto), PARAMS(args), PARAMS(fmt)) \ +static struct ftrace_event_call __used \ +__attribute__((__aligned__(4))) \ +__attribute__((section("_ftrace_events"))) event_##call = { \ + .name = #call, \ + .system = STR(TRACE_SYSTEM), \ + .regfunc = ftrace_reg_event_##call, \ + .unregfunc = ftrace_unreg_event_##call, \ +} + +#undef TRACE_FIELD +#define TRACE_FIELD(type, item, assign)\ + entry->item = assign; + +#undef TRACE_EVENT_FORMAT +#define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt) \ +_TRACE_FORMAT(call, PARAMS(proto), PARAMS(args), PARAMS(fmt)) \ + \ +static struct ftrace_event_call event_##call; \ + \ +static void ftrace_raw_event_##call(proto) \ +{ \ + struct ring_buffer_event *event; \ + struct ftrace_raw_##call *entry; \ + unsigned long irq_flags; \ + int pc; \ + \ + local_save_flags(irq_flags); \ + pc = preempt_count(); \ + \ + event = trace_current_buffer_lock_reserve(event_##call.id, \ + sizeof(struct ftrace_raw_##call), \ + irq_flags, pc); \ + if (!event) \ + return; \ + entry = ring_buffer_event_data(event); \ + \ + tstruct; \ + \ + trace_current_buffer_unlock_commit(event, irq_flags, pc); \ +} \ + \ +static int ftrace_raw_reg_event_##call(void) \ +{ \ + int ret; \ + \ + ret = register_trace_##call(ftrace_raw_event_##call); \ + if (!ret) \ + pr_info("event trace: Could not activate trace point " \ + "probe to " #call); \ + return ret; \ +} \ + \ +static void ftrace_raw_unreg_event_##call(void) \ +{ \ + unregister_trace_##call(ftrace_raw_event_##call); \ +} \ + \ +static struct trace_event ftrace_event_type_##call = { \ + .trace = ftrace_raw_output_##call, \ +}; \ + \ +static int ftrace_raw_init_event_##call(void) \ +{ \ + int id; \ + \ + id = register_ftrace_event(&ftrace_event_type_##call); \ + if (!id) \ + return -ENODEV; \ + event_##call.id = id; \ + return 0; \ +} \ + \ +static struct ftrace_event_call __used \ +__attribute__((__aligned__(4))) \ +__attribute__((section("_ftrace_events"))) event_##call = { \ + .name = #call, \ + .system = STR(TRACE_SYSTEM), \ + .regfunc = ftrace_reg_event_##call, \ + .unregfunc = ftrace_unreg_event_##call, \ + .raw_init = ftrace_raw_init_event_##call, \ + .raw_reg = ftrace_raw_reg_event_##call, \ + .raw_unreg = ftrace_raw_unreg_event_##call, \ +} -- 1.5.6.5 -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/