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Merge branch 'tip/perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into perf/core

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This commit is contained in:
Ingo Molnar 2010-07-23 09:10:29 +02:00
commit 3a01736e70
12 changed files with 242 additions and 34 deletions
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155
Documentation/trace/ftrace-design.txt
View File

@ -13,6 +13,9 @@ Note that this focuses on architecture implementation details only. If you
want more explanation of a feature in terms of common code, review the common
ftrace.txt file.
Ideally, everyone who wishes to retain performance while supporting tracing in
their kernel should make it all the way to dynamic ftrace support.
Prerequisites
-------------
@ -215,7 +218,7 @@ An arch may pass in a unique value (frame pointer) to both the entering and
exiting of a function. On exit, the value is compared and if it does not
match, then it will panic the kernel. This is largely a sanity check for bad
code generation with gcc. If gcc for your port sanely updates the frame
pointer under different opitmization levels, then ignore this option.
pointer under different optimization levels, then ignore this option.
However, adding support for it isn't terribly difficult. In your assembly code
that calls prepare_ftrace_return(), pass the frame pointer as the 3rd argument.
@ -234,7 +237,7 @@ If you can't trace NMI functions, then skip this option.
HAVE_SYSCALL_TRACEPOINTS
---------------------
------------------------
You need very few things to get the syscalls tracing in an arch.
@ -250,12 +253,152 @@ You need very few things to get the syscalls tracing in an arch.
HAVE_FTRACE_MCOUNT_RECORD
-------------------------
See scripts/recordmcount.pl for more info.
<details to be filled>
See scripts/recordmcount.pl for more info. Just fill in the arch-specific
details for how to locate the addresses of mcount call sites via objdump.
This option doesn't make much sense without also implementing dynamic ftrace.
HAVE_DYNAMIC_FTRACE
---------------------
-------------------
You will first need HAVE_FTRACE_MCOUNT_RECORD and HAVE_FUNCTION_TRACER, so
scroll your reader back up if you got over eager.
Once those are out of the way, you will need to implement:
- asm/ftrace.h:
- MCOUNT_ADDR
- ftrace_call_adjust()
- struct dyn_arch_ftrace{}
- asm code:
- mcount() (new stub)
- ftrace_caller()
- ftrace_call()
- ftrace_stub()
- C code:
- ftrace_dyn_arch_init()
- ftrace_make_nop()
- ftrace_make_call()
- ftrace_update_ftrace_func()
First you will need to fill out some arch details in your asm/ftrace.h.
Define MCOUNT_ADDR as the address of your mcount symbol similar to:
#define MCOUNT_ADDR ((unsigned long)mcount)
Since no one else will have a decl for that function, you will need to:
extern void mcount(void);
You will also need the helper function ftrace_call_adjust(). Most people
will be able to stub it out like so:
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
return addr;
}
<details to be filled>
Lastly you will need the custom dyn_arch_ftrace structure. If you need
some extra state when runtime patching arbitrary call sites, this is the
place. For now though, create an empty struct:
struct dyn_arch_ftrace {
/* No extra data needed */
};
With the header out of the way, we can fill out the assembly code. While we
did already create a mcount() function earlier, dynamic ftrace only wants a
stub function. This is because the mcount() will only be used during boot
and then all references to it will be patched out never to return. Instead,
the guts of the old mcount() will be used to create a new ftrace_caller()
function. Because the two are hard to merge, it will most likely be a lot
easier to have two separate definitions split up by #ifdefs. Same goes for
the ftrace_stub() as that will now be inlined in ftrace_caller().
Before we get confused anymore, let's check out some pseudo code so you can
implement your own stuff in assembly:
void mcount(void)
{
return;
}
void ftrace_caller(void)
{
/* implement HAVE_FUNCTION_TRACE_MCOUNT_TEST if you desire */
/* save all state needed by the ABI (see paragraph above) */
unsigned long frompc = ...;
unsigned long selfpc = <return address> - MCOUNT_INSN_SIZE;
ftrace_call:
ftrace_stub(frompc, selfpc);
/* restore all state needed by the ABI */
ftrace_stub:
return;
}
This might look a little odd at first, but keep in mind that we will be runtime
patching multiple things. First, only functions that we actually want to trace
will be patched to call ftrace_caller(). Second, since we only have one tracer
active at a time, we will patch the ftrace_caller() function itself to call the
specific tracer in question. That is the point of the ftrace_call label.
With that in mind, let's move on to the C code that will actually be doing the
runtime patching. You'll need a little knowledge of your arch's opcodes in
order to make it through the next section.
Every arch has an init callback function. If you need to do something early on
to initialize some state, this is the time to do that. Otherwise, this simple
function below should be sufficient for most people:
int __init ftrace_dyn_arch_init(void *data)
{
/* return value is done indirectly via data */
*(unsigned long *)data = 0;
return 0;
}
There are two functions that are used to do runtime patching of arbitrary
functions. The first is used to turn the mcount call site into a nop (which
is what helps us retain runtime performance when not tracing). The second is
used to turn the mcount call site into a call to an arbitrary location (but
typically that is ftracer_caller()). See the general function definition in
linux/ftrace.h for the functions:
ftrace_make_nop()
ftrace_make_call()
The rec->ip value is the address of the mcount call site that was collected
by the scripts/recordmcount.pl during build time.
The last function is used to do runtime patching of the active tracer. This
will be modifying the assembly code at the location of the ftrace_call symbol
inside of the ftrace_caller() function. So you should have sufficient padding
at that location to support the new function calls you'll be inserting. Some
people will be using a "call" type instruction while others will be using a
"branch" type instruction. Specifically, the function is:
ftrace_update_ftrace_func()
HAVE_DYNAMIC_FTRACE + HAVE_FUNCTION_GRAPH_TRACER
------------------------------------------------
The function grapher needs a few tweaks in order to work with dynamic ftrace.
Basically, you will need to:
- update:
- ftrace_caller()
- ftrace_graph_call()
- ftrace_graph_caller()
- implement:
- ftrace_enable_ftrace_graph_caller()
- ftrace_disable_ftrace_graph_caller()
<details to be filled>
Quick notes:
- add a nop stub after the ftrace_call location named ftrace_graph_call;
stub needs to be large enough to support a call to ftrace_graph_caller()
- update ftrace_graph_caller() to work with being called by the new
ftrace_caller() since some semantics may have changed
- ftrace_enable_ftrace_graph_caller() will runtime patch the
ftrace_graph_call location with a call to ftrace_graph_caller()
- ftrace_disable_ftrace_graph_caller() will runtime patch the
ftrace_graph_call location with nops

5
include/linux/ftrace.h
View File

@ -1,3 +1,8 @@
/*
* Ftrace header. For implementation details beyond the random comments
* scattered below, see: Documentation/trace/ftrace-design.txt
*/
#ifndef _LINUX_FTRACE_H
#define _LINUX_FTRACE_H

8
include/linux/ftrace_event.h
View File

@ -11,8 +11,6 @@ struct trace_array;
struct tracer;
struct dentry;
DECLARE_PER_CPU(struct trace_seq, ftrace_event_seq);
struct trace_print_flags {
unsigned long mask;
const char *name;
@ -58,6 +56,9 @@ struct trace_iterator {
struct ring_buffer_iter *buffer_iter[NR_CPUS];
unsigned long iter_flags;
/* trace_seq for __print_flags() and __print_symbolic() etc. */
struct trace_seq tmp_seq;
/* The below is zeroed out in pipe_read */
struct trace_seq seq;
struct trace_entry *ent;
@ -152,11 +153,13 @@ extern int ftrace_event_reg(struct ftrace_event_call *event,
enum {
TRACE_EVENT_FL_ENABLED_BIT,
TRACE_EVENT_FL_FILTERED_BIT,
TRACE_EVENT_FL_RECORDED_CMD_BIT,
};
enum {
TRACE_EVENT_FL_ENABLED = (1 << TRACE_EVENT_FL_ENABLED_BIT),
TRACE_EVENT_FL_FILTERED = (1 << TRACE_EVENT_FL_FILTERED_BIT),
TRACE_EVENT_FL_RECORDED_CMD = (1 << TRACE_EVENT_FL_RECORDED_CMD_BIT),
};
struct ftrace_event_call {
@ -174,6 +177,7 @@ struct ftrace_event_call {
* 32 bit flags:
* bit 1: enabled
* bit 2: filter_active
* bit 3: enabled cmd record
*
* Changes to flags must hold the event_mutex.
*

12
include/trace/ftrace.h
View File

@ -145,7 +145,7 @@
* struct trace_seq *s = &iter->seq;
* struct ftrace_raw_<call> *field; <-- defined in stage 1
* struct trace_entry *entry;
* struct trace_seq *p;
* struct trace_seq *p = &iter->tmp_seq;
* int ret;
*
* entry = iter->ent;
@ -157,12 +157,10 @@
*
* field = (typeof(field))entry;
*
* p = &get_cpu_var(ftrace_event_seq);
* trace_seq_init(p);
* ret = trace_seq_printf(s, "%s: ", <call>);
* if (ret)
* ret = trace_seq_printf(s, <TP_printk> "\n");
* put_cpu();
* if (!ret)
* return TRACE_TYPE_PARTIAL_LINE;
*
@ -216,7 +214,7 @@ 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; \
struct trace_seq *p; \
struct trace_seq *p = &iter->tmp_seq; \
int ret; \
\
event = container_of(trace_event, struct ftrace_event_call, \
@ -231,12 +229,10 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags, \
\
field = (typeof(field))entry; \
\
p = &get_cpu_var(ftrace_event_seq); \
trace_seq_init(p); \
ret = trace_seq_printf(s, "%s: ", event->name); \
if (ret) \
ret = trace_seq_printf(s, print); \
put_cpu(); \
if (!ret) \
return TRACE_TYPE_PARTIAL_LINE; \
\
@ -255,7 +251,7 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags, \
struct trace_seq *s = &iter->seq; \
struct ftrace_raw_##template *field; \
struct trace_entry *entry; \
struct trace_seq *p; \
struct trace_seq *p = &iter->tmp_seq; \
int ret; \
\
entry = iter->ent; \
@ -267,12 +263,10 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags, \
\
field = (typeof(field))entry; \
\
p = &get_cpu_var(ftrace_event_seq); \
trace_seq_init(p); \
ret = trace_seq_printf(s, "%s: ", #call); \
if (ret) \
ret = trace_seq_printf(s, print); \
put_cpu(); \
if (!ret) \
return TRACE_TYPE_PARTIAL_LINE; \
\

2
kernel/trace/ring_buffer.c
View File

@ -443,6 +443,7 @@ int ring_buffer_print_page_header(struct trace_seq *s)
*/
struct ring_buffer_per_cpu {
int cpu;
atomic_t record_disabled;
struct ring_buffer *buffer;
spinlock_t reader_lock; /* serialize readers */
arch_spinlock_t lock;
@ -462,7 +463,6 @@ struct ring_buffer_per_cpu {
unsigned long read;
u64 write_stamp;
u64 read_stamp;
atomic_t record_disabled;
};
struct ring_buffer {

46
kernel/trace/trace.c
View File

@ -344,7 +344,7 @@ static DECLARE_WAIT_QUEUE_HEAD(trace_wait);
/* trace_flags holds trace_options default values */
unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
TRACE_ITER_GRAPH_TIME;
TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD;
static int trace_stop_count;
static DEFINE_SPINLOCK(tracing_start_lock);
@ -428,6 +428,7 @@ static const char *trace_options[] = {
"latency-format",
"sleep-time",
"graph-time",
"record-cmd",
NULL
};
@ -659,6 +660,10 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
return;
WARN_ON_ONCE(!irqs_disabled());
if (!current_trace->use_max_tr) {
WARN_ON_ONCE(1);
return;
}
arch_spin_lock(&ftrace_max_lock);
tr->buffer = max_tr.buffer;
@ -685,6 +690,11 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
return;
WARN_ON_ONCE(!irqs_disabled());
if (!current_trace->use_max_tr) {
WARN_ON_ONCE(1);
return;
}
arch_spin_lock(&ftrace_max_lock);
ftrace_disable_cpu();
@ -729,7 +739,7 @@ __acquires(kernel_lock)
return -1;
}
if (strlen(type->name) > MAX_TRACER_SIZE) {
if (strlen(type->name) >= MAX_TRACER_SIZE) {
pr_info("Tracer has a name longer than %d\n", MAX_TRACER_SIZE);
return -1;
}
@ -2508,6 +2518,9 @@ static void set_tracer_flags(unsigned int mask, int enabled)
trace_flags |= mask;
else
trace_flags &= ~mask;
if (mask == TRACE_ITER_RECORD_CMD)
trace_event_enable_cmd_record(enabled);
}
static ssize_t
@ -2746,6 +2759,9 @@ static int tracing_resize_ring_buffer(unsigned long size)
if (ret < 0)
return ret;
if (!current_trace->use_max_tr)
goto out;
ret = ring_buffer_resize(max_tr.buffer, size);
if (ret < 0) {
int r;
@ -2773,11 +2789,14 @@ static int tracing_resize_ring_buffer(unsigned long size)
return ret;
}
max_tr.entries = size;
out:
global_trace.entries = size;
return ret;
}
/**
* tracing_update_buffers - used by tracing facility to expand ring buffers
*
@ -2838,12 +2857,26 @@ static int tracing_set_tracer(const char *buf)
trace_branch_disable();
if (current_trace && current_trace->reset)
current_trace->reset(tr);
if (current_trace && current_trace->use_max_tr) {
/*
* We don't free the ring buffer. instead, resize it because
* The max_tr ring buffer has some state (e.g. ring->clock) and
* we want preserve it.
*/
ring_buffer_resize(max_tr.buffer, 1);
max_tr.entries = 1;
}
destroy_trace_option_files(topts);
current_trace = t;
topts = create_trace_option_files(current_trace);
if (current_trace->use_max_tr) {
ret = ring_buffer_resize(max_tr.buffer, global_trace.entries);
if (ret < 0)
goto out;
max_tr.entries = global_trace.entries;
}
if (t->init) {
ret = tracer_init(t, tr);
@ -3426,7 +3459,6 @@ tracing_entries_write(struct file *filp, const char __user *ubuf,
}
tracing_start();
max_tr.entries = global_trace.entries;
mutex_unlock(&trace_types_lock);
return cnt;
@ -4531,16 +4563,14 @@ __init static int tracer_alloc_buffers(void)
#ifdef CONFIG_TRACER_MAX_TRACE
max_tr.buffer = ring_buffer_alloc(ring_buf_size,
TRACE_BUFFER_FLAGS);
max_tr.buffer = ring_buffer_alloc(1, TRACE_BUFFER_FLAGS);
if (!max_tr.buffer) {
printk(KERN_ERR "tracer: failed to allocate max ring buffer!\n");
WARN_ON(1);
ring_buffer_free(global_trace.buffer);
goto out_free_cpumask;
}
max_tr.entries = ring_buffer_size(max_tr.buffer);
WARN_ON(max_tr.entries != global_trace.entries);
max_tr.entries = 1;
#endif
/* Allocate the first page for all buffers */

4
kernel/trace/trace.h
View File

@ -274,6 +274,7 @@ struct tracer {
struct tracer *next;
int print_max;
struct tracer_flags *flags;
int use_max_tr;
};
@ -581,6 +582,7 @@ enum trace_iterator_flags {
TRACE_ITER_LATENCY_FMT = 0x20000,
TRACE_ITER_SLEEP_TIME = 0x40000,
TRACE_ITER_GRAPH_TIME = 0x80000,
TRACE_ITER_RECORD_CMD = 0x100000,
};
/*
@ -713,6 +715,8 @@ filter_check_discard(struct ftrace_event_call *call, void *rec,
return 0;
}
extern void trace_event_enable_cmd_record(bool enable);
extern struct mutex event_mutex;
extern struct list_head ftrace_events;

26
kernel/trace/trace_events.c
View File

@ -170,6 +170,26 @@ int ftrace_event_reg(struct ftrace_event_call *call, enum trace_reg type)
}
EXPORT_SYMBOL_GPL(ftrace_event_reg);
void trace_event_enable_cmd_record(bool enable)
{
struct ftrace_event_call *call;
mutex_lock(&event_mutex);
list_for_each_entry(call, &ftrace_events, list) {
if (!(call->flags & TRACE_EVENT_FL_ENABLED))
continue;
if (enable) {
tracing_start_cmdline_record();
call->flags |= TRACE_EVENT_FL_RECORDED_CMD;
} else {
tracing_stop_cmdline_record();
call->flags &= ~TRACE_EVENT_FL_RECORDED_CMD;
}
}
mutex_unlock(&event_mutex);
}
static int ftrace_event_enable_disable(struct ftrace_event_call *call,
int enable)
{
@ -179,13 +199,19 @@ static int ftrace_event_enable_disable(struct ftrace_event_call *call,
case 0:
if (call->flags & TRACE_EVENT_FL_ENABLED) {
call->flags &= ~TRACE_EVENT_FL_ENABLED;
if (call->flags & TRACE_EVENT_FL_RECORDED_CMD) {
tracing_stop_cmdline_record();
call->flags &= ~TRACE_EVENT_FL_RECORDED_CMD;
}
call->class->reg(call, TRACE_REG_UNREGISTER);
}
break;
case 1:
if (!(call->flags & TRACE_EVENT_FL_ENABLED)) {
if (trace_flags & TRACE_ITER_RECORD_CMD) {
tracing_start_cmdline_record();
call->flags |= TRACE_EVENT_FL_RECORDED_CMD;
}
ret = call->class->reg(call, TRACE_REG_REGISTER);
if (ret) {
tracing_stop_cmdline_record();

3
kernel/trace/trace_irqsoff.c
View File

@ -649,6 +649,7 @@ static struct tracer irqsoff_tracer __read_mostly =
#endif
.open = irqsoff_trace_open,
.close = irqsoff_trace_close,
.use_max_tr = 1,
};
# define register_irqsoff(trace) register_tracer(&trace)
#else
@ -681,6 +682,7 @@ static struct tracer preemptoff_tracer __read_mostly =
#endif
.open = irqsoff_trace_open,
.close = irqsoff_trace_close,
.use_max_tr = 1,
};
# define register_preemptoff(trace) register_tracer(&trace)
#else
@ -715,6 +717,7 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
#endif
.open = irqsoff_trace_open,
.close = irqsoff_trace_close,
.use_max_tr = 1,
};
# define register_preemptirqsoff(trace) register_tracer(&trace)

3
kernel/trace/trace_output.c
View File

@ -16,9 +16,6 @@
DECLARE_RWSEM(trace_event_mutex);
DEFINE_PER_CPU(struct trace_seq, ftrace_event_seq);
EXPORT_PER_CPU_SYMBOL(ftrace_event_seq);
static struct hlist_head event_hash[EVENT_HASHSIZE] __read_mostly;
static int next_event_type = __TRACE_LAST_TYPE + 1;

2
kernel/trace/trace_sched_wakeup.c
View File

@ -382,6 +382,7 @@ static struct tracer wakeup_tracer __read_mostly =
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
.use_max_tr = 1,
};
static struct tracer wakeup_rt_tracer __read_mostly =
@ -396,6 +397,7 @@ static struct tracer wakeup_rt_tracer __read_mostly =
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
.use_max_tr = 1,
};
__init static int init_wakeup_tracer(void)

2
scripts/recordmcount.pl
View File

@ -326,7 +326,7 @@ if ($arch eq "x86_64") {
# 14: R_MIPS_NONE *ABS*
# 18: 00020021 nop
if ($is_module eq "0") {
$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
$mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_26\\s+_mcount\$";
} else {
$mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
}