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linux-next/drivers/oprofile/cpu_buffer.c

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/**
* @file cpu_buffer.c
*
* @remark Copyright 2002 OProfile authors
* @remark Read the file COPYING
*
* @author John Levon <levon@movementarian.org>
* @author Barry Kasindorf <barry.kasindorf@amd.com>
*
* Each CPU has a local buffer that stores PC value/event
* pairs. We also log context switches when we notice them.
* Eventually each CPU's buffer is processed into the global
* event buffer by sync_buffer().
*
* We use a local buffer for two reasons: an NMI or similar
* interrupt cannot synchronise, and high sampling rates
* would lead to catastrophic global synchronisation if
* a global buffer was used.
*/
#include <linux/sched.h>
#include <linux/oprofile.h>
#include <linux/vmalloc.h>
#include <linux/errno.h>
#include "event_buffer.h"
#include "cpu_buffer.h"
#include "buffer_sync.h"
#include "oprof.h"
oprofile: port to the new ring_buffer This patch replaces the current oprofile cpu buffer implementation with the ring buffer provided by the tracing framework. The motivation here is to leave the pain of implementing ring buffers to others. Oh, no, there are more advantages. Main reason is the support of different sample sizes that could be stored in the buffer. Use cases for this are IBS and Cell spu profiling. Using the new ring buffer ensures valid and complete samples and allows copying the cpu buffer stateless without knowing its content. Second it will use generic kernel API and also reduce code size. And hopefully, there are less bugs. Since the new tracing ring buffer implementation uses spin locks to protect the buffer during read/write access, it is difficult to use the buffer in an NMI handler. In this case, writing to the buffer by the NMI handler (x86) could occur also during critical sections when reading the buffer. To avoid this, there are 2 buffers for independent read and write access. Read access is in process context only, write access only in the NMI handler. If the read buffer runs empty, both buffers are swapped atomically. There is potentially a small window during swapping where the buffers are disabled and samples could be lost. Using 2 buffers is a little bit overhead, but the solution is clear and does not require changes in the ring buffer implementation. It can be changed to a single buffer solution when the ring buffer access is implemented as non-locking atomic code. The new buffer requires more size to store the same amount of samples because each sample includes an u32 header. Also, there is more code to execute for buffer access. Nonetheless, the buffer implementation is proven in the ftrace environment and worth to use also in oprofile. Patches that changes the internal IBS buffer usage will follow. Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Robert Richter <robert.richter@amd.com>
2008-12-09 08:21:32 +08:00
#define OP_BUFFER_FLAGS 0
/*
* Read and write access is using spin locking. Thus, writing to the
* buffer by NMI handler (x86) could occur also during critical
* sections when reading the buffer. To avoid this, there are 2
* buffers for independent read and write access. Read access is in
* process context only, write access only in the NMI handler. If the
* read buffer runs empty, both buffers are swapped atomically. There
* is potentially a small window during swapping where the buffers are
* disabled and samples could be lost.
*
* Using 2 buffers is a little bit overhead, but the solution is clear
* and does not require changes in the ring buffer implementation. It
* can be changed to a single buffer solution when the ring buffer
* access is implemented as non-locking atomic code.
*/
static struct ring_buffer *op_ring_buffer_read;
static struct ring_buffer *op_ring_buffer_write;
DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
static void wq_sync_buffer(struct work_struct *work);
#define DEFAULT_TIMER_EXPIRE (HZ / 10)
static int work_enabled;
unsigned long oprofile_get_cpu_buffer_size(void)
{
return oprofile_cpu_buffer_size;
}
void oprofile_cpu_buffer_inc_smpl_lost(void)
{
struct oprofile_cpu_buffer *cpu_buf
= &__get_cpu_var(cpu_buffer);
cpu_buf->sample_lost_overflow++;
}
void free_cpu_buffers(void)
{
if (op_ring_buffer_read)
ring_buffer_free(op_ring_buffer_read);
op_ring_buffer_read = NULL;
if (op_ring_buffer_write)
ring_buffer_free(op_ring_buffer_write);
op_ring_buffer_write = NULL;
}
int alloc_cpu_buffers(void)
{
int i;
unsigned long buffer_size = oprofile_cpu_buffer_size;
oprofile: port to the new ring_buffer This patch replaces the current oprofile cpu buffer implementation with the ring buffer provided by the tracing framework. The motivation here is to leave the pain of implementing ring buffers to others. Oh, no, there are more advantages. Main reason is the support of different sample sizes that could be stored in the buffer. Use cases for this are IBS and Cell spu profiling. Using the new ring buffer ensures valid and complete samples and allows copying the cpu buffer stateless without knowing its content. Second it will use generic kernel API and also reduce code size. And hopefully, there are less bugs. Since the new tracing ring buffer implementation uses spin locks to protect the buffer during read/write access, it is difficult to use the buffer in an NMI handler. In this case, writing to the buffer by the NMI handler (x86) could occur also during critical sections when reading the buffer. To avoid this, there are 2 buffers for independent read and write access. Read access is in process context only, write access only in the NMI handler. If the read buffer runs empty, both buffers are swapped atomically. There is potentially a small window during swapping where the buffers are disabled and samples could be lost. Using 2 buffers is a little bit overhead, but the solution is clear and does not require changes in the ring buffer implementation. It can be changed to a single buffer solution when the ring buffer access is implemented as non-locking atomic code. The new buffer requires more size to store the same amount of samples because each sample includes an u32 header. Also, there is more code to execute for buffer access. Nonetheless, the buffer implementation is proven in the ftrace environment and worth to use also in oprofile. Patches that changes the internal IBS buffer usage will follow. Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Robert Richter <robert.richter@amd.com>
2008-12-09 08:21:32 +08:00
op_ring_buffer_read = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
if (!op_ring_buffer_read)
goto fail;
op_ring_buffer_write = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
if (!op_ring_buffer_write)
goto fail;
for_each_possible_cpu(i) {
struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
b->last_task = NULL;
b->last_is_kernel = -1;
b->tracing = 0;
b->buffer_size = buffer_size;
b->tail_pos = 0;
b->head_pos = 0;
b->sample_received = 0;
b->sample_lost_overflow = 0;
b->backtrace_aborted = 0;
b->sample_invalid_eip = 0;
b->cpu = i;
INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
}
return 0;
fail:
free_cpu_buffers();
return -ENOMEM;
}
void start_cpu_work(void)
{
int i;
work_enabled = 1;
for_each_online_cpu(i) {
struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
/*
* Spread the work by 1 jiffy per cpu so they dont all
* fire at once.
*/
schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
}
}
void end_cpu_work(void)
{
int i;
work_enabled = 0;
for_each_online_cpu(i) {
struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
cancel_delayed_work(&b->work);
}
flush_scheduled_work();
}
int op_cpu_buffer_write_entry(struct op_entry *entry)
{
entry->event = ring_buffer_lock_reserve(op_ring_buffer_write,
sizeof(struct op_sample),
&entry->irq_flags);
if (entry->event)
entry->sample = ring_buffer_event_data(entry->event);
else
entry->sample = NULL;
if (!entry->sample)
return -ENOMEM;
return 0;
}
int op_cpu_buffer_write_commit(struct op_entry *entry)
{
return ring_buffer_unlock_commit(op_ring_buffer_write, entry->event,
entry->irq_flags);
}
struct op_sample *op_cpu_buffer_read_entry(int cpu)
{
struct ring_buffer_event *e;
e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
if (e)
return ring_buffer_event_data(e);
if (ring_buffer_swap_cpu(op_ring_buffer_read,
op_ring_buffer_write,
cpu))
return NULL;
e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
if (e)
return ring_buffer_event_data(e);
return NULL;
}
unsigned long op_cpu_buffer_entries(int cpu)
{
return ring_buffer_entries_cpu(op_ring_buffer_read, cpu)
+ ring_buffer_entries_cpu(op_ring_buffer_write, cpu);
}
static inline int
add_sample(struct oprofile_cpu_buffer *cpu_buf,
unsigned long pc, unsigned long event)
{
oprofile: port to the new ring_buffer This patch replaces the current oprofile cpu buffer implementation with the ring buffer provided by the tracing framework. The motivation here is to leave the pain of implementing ring buffers to others. Oh, no, there are more advantages. Main reason is the support of different sample sizes that could be stored in the buffer. Use cases for this are IBS and Cell spu profiling. Using the new ring buffer ensures valid and complete samples and allows copying the cpu buffer stateless without knowing its content. Second it will use generic kernel API and also reduce code size. And hopefully, there are less bugs. Since the new tracing ring buffer implementation uses spin locks to protect the buffer during read/write access, it is difficult to use the buffer in an NMI handler. In this case, writing to the buffer by the NMI handler (x86) could occur also during critical sections when reading the buffer. To avoid this, there are 2 buffers for independent read and write access. Read access is in process context only, write access only in the NMI handler. If the read buffer runs empty, both buffers are swapped atomically. There is potentially a small window during swapping where the buffers are disabled and samples could be lost. Using 2 buffers is a little bit overhead, but the solution is clear and does not require changes in the ring buffer implementation. It can be changed to a single buffer solution when the ring buffer access is implemented as non-locking atomic code. The new buffer requires more size to store the same amount of samples because each sample includes an u32 header. Also, there is more code to execute for buffer access. Nonetheless, the buffer implementation is proven in the ftrace environment and worth to use also in oprofile. Patches that changes the internal IBS buffer usage will follow. Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Robert Richter <robert.richter@amd.com>
2008-12-09 08:21:32 +08:00
struct op_entry entry;
int ret;
oprofile: port to the new ring_buffer This patch replaces the current oprofile cpu buffer implementation with the ring buffer provided by the tracing framework. The motivation here is to leave the pain of implementing ring buffers to others. Oh, no, there are more advantages. Main reason is the support of different sample sizes that could be stored in the buffer. Use cases for this are IBS and Cell spu profiling. Using the new ring buffer ensures valid and complete samples and allows copying the cpu buffer stateless without knowing its content. Second it will use generic kernel API and also reduce code size. And hopefully, there are less bugs. Since the new tracing ring buffer implementation uses spin locks to protect the buffer during read/write access, it is difficult to use the buffer in an NMI handler. In this case, writing to the buffer by the NMI handler (x86) could occur also during critical sections when reading the buffer. To avoid this, there are 2 buffers for independent read and write access. Read access is in process context only, write access only in the NMI handler. If the read buffer runs empty, both buffers are swapped atomically. There is potentially a small window during swapping where the buffers are disabled and samples could be lost. Using 2 buffers is a little bit overhead, but the solution is clear and does not require changes in the ring buffer implementation. It can be changed to a single buffer solution when the ring buffer access is implemented as non-locking atomic code. The new buffer requires more size to store the same amount of samples because each sample includes an u32 header. Also, there is more code to execute for buffer access. Nonetheless, the buffer implementation is proven in the ftrace environment and worth to use also in oprofile. Patches that changes the internal IBS buffer usage will follow. Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Robert Richter <robert.richter@amd.com>
2008-12-09 08:21:32 +08:00
ret = op_cpu_buffer_write_entry(&entry);
if (ret)
return ret;
oprofile: port to the new ring_buffer This patch replaces the current oprofile cpu buffer implementation with the ring buffer provided by the tracing framework. The motivation here is to leave the pain of implementing ring buffers to others. Oh, no, there are more advantages. Main reason is the support of different sample sizes that could be stored in the buffer. Use cases for this are IBS and Cell spu profiling. Using the new ring buffer ensures valid and complete samples and allows copying the cpu buffer stateless without knowing its content. Second it will use generic kernel API and also reduce code size. And hopefully, there are less bugs. Since the new tracing ring buffer implementation uses spin locks to protect the buffer during read/write access, it is difficult to use the buffer in an NMI handler. In this case, writing to the buffer by the NMI handler (x86) could occur also during critical sections when reading the buffer. To avoid this, there are 2 buffers for independent read and write access. Read access is in process context only, write access only in the NMI handler. If the read buffer runs empty, both buffers are swapped atomically. There is potentially a small window during swapping where the buffers are disabled and samples could be lost. Using 2 buffers is a little bit overhead, but the solution is clear and does not require changes in the ring buffer implementation. It can be changed to a single buffer solution when the ring buffer access is implemented as non-locking atomic code. The new buffer requires more size to store the same amount of samples because each sample includes an u32 header. Also, there is more code to execute for buffer access. Nonetheless, the buffer implementation is proven in the ftrace environment and worth to use also in oprofile. Patches that changes the internal IBS buffer usage will follow. Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Robert Richter <robert.richter@amd.com>
2008-12-09 08:21:32 +08:00
entry.sample->eip = pc;
entry.sample->event = event;
ret = op_cpu_buffer_write_commit(&entry);
if (ret)
return ret;
oprofile: port to the new ring_buffer This patch replaces the current oprofile cpu buffer implementation with the ring buffer provided by the tracing framework. The motivation here is to leave the pain of implementing ring buffers to others. Oh, no, there are more advantages. Main reason is the support of different sample sizes that could be stored in the buffer. Use cases for this are IBS and Cell spu profiling. Using the new ring buffer ensures valid and complete samples and allows copying the cpu buffer stateless without knowing its content. Second it will use generic kernel API and also reduce code size. And hopefully, there are less bugs. Since the new tracing ring buffer implementation uses spin locks to protect the buffer during read/write access, it is difficult to use the buffer in an NMI handler. In this case, writing to the buffer by the NMI handler (x86) could occur also during critical sections when reading the buffer. To avoid this, there are 2 buffers for independent read and write access. Read access is in process context only, write access only in the NMI handler. If the read buffer runs empty, both buffers are swapped atomically. There is potentially a small window during swapping where the buffers are disabled and samples could be lost. Using 2 buffers is a little bit overhead, but the solution is clear and does not require changes in the ring buffer implementation. It can be changed to a single buffer solution when the ring buffer access is implemented as non-locking atomic code. The new buffer requires more size to store the same amount of samples because each sample includes an u32 header. Also, there is more code to execute for buffer access. Nonetheless, the buffer implementation is proven in the ftrace environment and worth to use also in oprofile. Patches that changes the internal IBS buffer usage will follow. Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Robert Richter <robert.richter@amd.com>
2008-12-09 08:21:32 +08:00
return 0;
}
static inline int
add_code(struct oprofile_cpu_buffer *buffer, unsigned long value)
{
return add_sample(buffer, ESCAPE_CODE, value);
}
/* This must be safe from any context. It's safe writing here
* because of the head/tail separation of the writer and reader
* of the CPU buffer.
*
* is_kernel is needed because on some architectures you cannot
* tell if you are in kernel or user space simply by looking at
* pc. We tag this in the buffer by generating kernel enter/exit
* events whenever is_kernel changes
*/
static int log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc,
int is_kernel, unsigned long event)
{
struct task_struct *task;
cpu_buf->sample_received++;
if (pc == ESCAPE_CODE) {
cpu_buf->sample_invalid_eip++;
return 0;
}
is_kernel = !!is_kernel;
task = current;
/* notice a switch from user->kernel or vice versa */
if (cpu_buf->last_is_kernel != is_kernel) {
cpu_buf->last_is_kernel = is_kernel;
if (add_code(cpu_buf, is_kernel))
goto fail;
}
/* notice a task switch */
if (cpu_buf->last_task != task) {
cpu_buf->last_task = task;
if (add_code(cpu_buf, (unsigned long)task))
goto fail;
}
if (add_sample(cpu_buf, pc, event))
goto fail;
return 1;
fail:
cpu_buf->sample_lost_overflow++;
return 0;
}
static int oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf)
{
add_code(cpu_buf, CPU_TRACE_BEGIN);
cpu_buf->tracing = 1;
return 1;
}
static void oprofile_end_trace(struct oprofile_cpu_buffer *cpu_buf)
{
cpu_buf->tracing = 0;
}
static inline void
__oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
unsigned long event, int is_kernel)
{
struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
if (!oprofile_backtrace_depth) {
log_sample(cpu_buf, pc, is_kernel, event);
return;
}
if (!oprofile_begin_trace(cpu_buf))
return;
/*
* if log_sample() fail we can't backtrace since we lost the
* source of this event
*/
if (log_sample(cpu_buf, pc, is_kernel, event))
oprofile_ops.backtrace(regs, oprofile_backtrace_depth);
oprofile_end_trace(cpu_buf);
}
void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
unsigned long event, int is_kernel)
{
__oprofile_add_ext_sample(pc, regs, event, is_kernel);
}
void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
{
int is_kernel = !user_mode(regs);
unsigned long pc = profile_pc(regs);
__oprofile_add_ext_sample(pc, regs, event, is_kernel);
}
#ifdef CONFIG_OPROFILE_IBS
#define MAX_IBS_SAMPLE_SIZE 14
void oprofile_add_ibs_sample(struct pt_regs * const regs,
unsigned int * const ibs_sample, int ibs_code)
{
int is_kernel = !user_mode(regs);
struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
struct task_struct *task;
int fail = 0;
cpu_buf->sample_received++;
/* notice a switch from user->kernel or vice versa */
if (cpu_buf->last_is_kernel != is_kernel) {
if (add_code(cpu_buf, is_kernel))
goto fail;
cpu_buf->last_is_kernel = is_kernel;
}
/* notice a task switch */
if (!is_kernel) {
task = current;
if (cpu_buf->last_task != task) {
if (add_code(cpu_buf, (unsigned long)task))
goto fail;
cpu_buf->last_task = task;
}
}
fail = fail || add_code(cpu_buf, ibs_code);
fail = fail || add_sample(cpu_buf, ibs_sample[0], ibs_sample[1]);
fail = fail || add_sample(cpu_buf, ibs_sample[2], ibs_sample[3]);
fail = fail || add_sample(cpu_buf, ibs_sample[4], ibs_sample[5]);
if (ibs_code == IBS_OP_BEGIN) {
fail = fail || add_sample(cpu_buf, ibs_sample[6], ibs_sample[7]);
fail = fail || add_sample(cpu_buf, ibs_sample[8], ibs_sample[9]);
fail = fail || add_sample(cpu_buf, ibs_sample[10], ibs_sample[11]);
}
if (fail)
goto fail;
if (oprofile_backtrace_depth)
oprofile_ops.backtrace(regs, oprofile_backtrace_depth);
return;
fail:
cpu_buf->sample_lost_overflow++;
return;
}
#endif
void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event)
{
struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
log_sample(cpu_buf, pc, is_kernel, event);
}
void oprofile_add_trace(unsigned long pc)
{
struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
if (!cpu_buf->tracing)
return;
/*
* broken frame can give an eip with the same value as an
* escape code, abort the trace if we get it
*/
if (pc == ESCAPE_CODE)
goto fail;
if (add_sample(cpu_buf, pc, 0))
goto fail;
return;
fail:
cpu_buf->tracing = 0;
cpu_buf->backtrace_aborted++;
return;
}
/*
* This serves to avoid cpu buffer overflow, and makes sure
* the task mortuary progresses
*
* By using schedule_delayed_work_on and then schedule_delayed_work
* we guarantee this will stay on the correct cpu
*/
static void wq_sync_buffer(struct work_struct *work)
{
struct oprofile_cpu_buffer *b =
container_of(work, struct oprofile_cpu_buffer, work.work);
if (b->cpu != smp_processor_id()) {
printk(KERN_DEBUG "WQ on CPU%d, prefer CPU%d\n",
smp_processor_id(), b->cpu);
if (!cpu_online(b->cpu)) {
cancel_delayed_work(&b->work);
return;
}
}
sync_buffer(b->cpu);
/* don't re-add the work if we're shutting down */
if (work_enabled)
schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
}