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authorRobert Richter <robert.richter@amd.com>2008-12-09 03:21:32 +0300
committerRobert Richter <robert.richter@amd.com>2008-12-10 16:20:18 +0300
commit6dad828b76c7224a22ddc9ce7aa495d994f03b31 (patch)
tree364de7a3efd56d60c0742145e3a8d3d4f73bcde4 /drivers/oprofile/buffer_sync.c
parente09373f22e76cc048ca5fe10a9ff9012f5d64309 (diff)
downloadlinux-6dad828b76c7224a22ddc9ce7aa495d994f03b31.tar.xz
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>
Diffstat (limited to 'drivers/oprofile/buffer_sync.c')
-rw-r--r--drivers/oprofile/buffer_sync.c65
1 files changed, 25 insertions, 40 deletions
diff --git a/drivers/oprofile/buffer_sync.c b/drivers/oprofile/buffer_sync.c
index 944a5832d9e4..737bd9484822 100644
--- a/drivers/oprofile/buffer_sync.c
+++ b/drivers/oprofile/buffer_sync.c
@@ -268,18 +268,6 @@ lookup_dcookie(struct mm_struct *mm, unsigned long addr, off_t *offset)
return cookie;
}
-static void increment_tail(struct oprofile_cpu_buffer *b)
-{
- unsigned long new_tail = b->tail_pos + 1;
-
- rmb(); /* be sure fifo pointers are synchronized */
-
- if (new_tail < b->buffer_size)
- b->tail_pos = new_tail;
- else
- b->tail_pos = 0;
-}
-
static unsigned long last_cookie = INVALID_COOKIE;
static void add_cpu_switch(int i)
@@ -331,26 +319,25 @@ static void add_trace_begin(void)
#define IBS_FETCH_CODE_SIZE 2
#define IBS_OP_CODE_SIZE 5
-#define IBS_EIP(cpu_buf) ((cpu_buffer_read_entry(cpu_buf))->eip)
-#define IBS_EVENT(cpu_buf) ((cpu_buffer_read_entry(cpu_buf))->event)
/*
* Add IBS fetch and op entries to event buffer
*/
-static void add_ibs_begin(struct oprofile_cpu_buffer *cpu_buf, int code,
- struct mm_struct *mm)
+static void add_ibs_begin(int cpu, int code, struct mm_struct *mm)
{
unsigned long rip;
int i, count;
unsigned long ibs_cookie = 0;
off_t offset;
+ struct op_sample *sample;
- increment_tail(cpu_buf); /* move to RIP entry */
-
- rip = IBS_EIP(cpu_buf);
+ sample = cpu_buffer_read_entry(cpu);
+ if (!sample)
+ goto Error;
+ rip = sample->eip;
#ifdef __LP64__
- rip += IBS_EVENT(cpu_buf) << 32;
+ rip += sample->event << 32;
#endif
if (mm) {
@@ -374,8 +361,8 @@ static void add_ibs_begin(struct oprofile_cpu_buffer *cpu_buf, int code,
add_event_entry(offset); /* Offset from Dcookie */
/* we send the Dcookie offset, but send the raw Linear Add also*/
- add_event_entry(IBS_EIP(cpu_buf));
- add_event_entry(IBS_EVENT(cpu_buf));
+ add_event_entry(sample->eip);
+ add_event_entry(sample->event);
if (code == IBS_FETCH_CODE)
count = IBS_FETCH_CODE_SIZE; /*IBS FETCH is 2 int64s*/
@@ -383,10 +370,17 @@ static void add_ibs_begin(struct oprofile_cpu_buffer *cpu_buf, int code,
count = IBS_OP_CODE_SIZE; /*IBS OP is 5 int64s*/
for (i = 0; i < count; i++) {
- increment_tail(cpu_buf);
- add_event_entry(IBS_EIP(cpu_buf));
- add_event_entry(IBS_EVENT(cpu_buf));
+ sample = cpu_buffer_read_entry(cpu);
+ if (!sample)
+ goto Error;
+ add_event_entry(sample->eip);
+ add_event_entry(sample->event);
}
+
+ return;
+
+Error:
+ return;
}
#endif
@@ -530,33 +524,26 @@ typedef enum {
*/
void sync_buffer(int cpu)
{
- struct oprofile_cpu_buffer *cpu_buf = &per_cpu(cpu_buffer, cpu);
struct mm_struct *mm = NULL;
struct mm_struct *oldmm;
struct task_struct *new;
unsigned long cookie = 0;
int in_kernel = 1;
sync_buffer_state state = sb_buffer_start;
-#ifndef CONFIG_OPROFILE_IBS
unsigned int i;
unsigned long available;
-#endif
mutex_lock(&buffer_mutex);
add_cpu_switch(cpu);
- /* Remember, only we can modify tail_pos */
-
cpu_buffer_reset(cpu);
-#ifndef CONFIG_OPROFILE_IBS
- available = cpu_buffer_entries(cpu_buf);
+ available = cpu_buffer_entries(cpu);
for (i = 0; i < available; ++i) {
-#else
- while (cpu_buffer_entries(cpu_buf)) {
-#endif
- struct op_sample *s = cpu_buffer_read_entry(cpu_buf);
+ struct op_sample *s = cpu_buffer_read_entry(cpu);
+ if (!s)
+ break;
if (is_code(s->eip)) {
switch (s->event) {
@@ -575,11 +562,11 @@ void sync_buffer(int cpu)
#ifdef CONFIG_OPROFILE_IBS
case IBS_FETCH_BEGIN:
state = sb_bt_start;
- add_ibs_begin(cpu_buf, IBS_FETCH_CODE, mm);
+ add_ibs_begin(cpu, IBS_FETCH_CODE, mm);
break;
case IBS_OP_BEGIN:
state = sb_bt_start;
- add_ibs_begin(cpu_buf, IBS_OP_CODE, mm);
+ add_ibs_begin(cpu, IBS_OP_CODE, mm);
break;
#endif
default:
@@ -600,8 +587,6 @@ void sync_buffer(int cpu)
atomic_inc(&oprofile_stats.bt_lost_no_mapping);
}
}
-
- increment_tail(cpu_buf);
}
release_mm(mm);