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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /drivers/oprofile/cpu_buffer.c | |
download | linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.bz2 |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'drivers/oprofile/cpu_buffer.c')
-rw-r--r-- | drivers/oprofile/cpu_buffer.c | 307 |
1 files changed, 307 insertions, 0 deletions
diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c new file mode 100644 index 000000000000..e9b1772a3a28 --- /dev/null +++ b/drivers/oprofile/cpu_buffer.c @@ -0,0 +1,307 @@ +/** + * @file cpu_buffer.c + * + * @remark Copyright 2002 OProfile authors + * @remark Read the file COPYING + * + * @author John Levon <levon@movementarian.org> + * + * 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" + +struct oprofile_cpu_buffer cpu_buffer[NR_CPUS] __cacheline_aligned; + +static void wq_sync_buffer(void *); + +#define DEFAULT_TIMER_EXPIRE (HZ / 10) +static int work_enabled; + +void free_cpu_buffers(void) +{ + int i; + + for_each_online_cpu(i) { + vfree(cpu_buffer[i].buffer); + } +} + + +int alloc_cpu_buffers(void) +{ + int i; + + unsigned long buffer_size = fs_cpu_buffer_size; + + for_each_online_cpu(i) { + struct oprofile_cpu_buffer * b = &cpu_buffer[i]; + + b->buffer = vmalloc(sizeof(struct op_sample) * buffer_size); + if (!b->buffer) + goto fail; + + 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->cpu = i; + INIT_WORK(&b->work, wq_sync_buffer, b); + } + 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 = &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 = &cpu_buffer[i]; + + cancel_delayed_work(&b->work); + } + + flush_scheduled_work(); +} + + +/* Resets the cpu buffer to a sane state. */ +void cpu_buffer_reset(struct oprofile_cpu_buffer * cpu_buf) +{ + /* reset these to invalid values; the next sample + * collected will populate the buffer with proper + * values to initialize the buffer + */ + cpu_buf->last_is_kernel = -1; + cpu_buf->last_task = NULL; +} + + +/* compute number of available slots in cpu_buffer queue */ +static unsigned long nr_available_slots(struct oprofile_cpu_buffer const * b) +{ + unsigned long head = b->head_pos; + unsigned long tail = b->tail_pos; + + if (tail > head) + return (tail - head) - 1; + + return tail + (b->buffer_size - head) - 1; +} + + +static void increment_head(struct oprofile_cpu_buffer * b) +{ + unsigned long new_head = b->head_pos + 1; + + /* Ensure anything written to the slot before we + * increment is visible */ + wmb(); + + if (new_head < b->buffer_size) + b->head_pos = new_head; + else + b->head_pos = 0; +} + + + + +inline static void +add_sample(struct oprofile_cpu_buffer * cpu_buf, + unsigned long pc, unsigned long event) +{ + struct op_sample * entry = &cpu_buf->buffer[cpu_buf->head_pos]; + entry->eip = pc; + entry->event = event; + increment_head(cpu_buf); +} + + +inline static void +add_code(struct oprofile_cpu_buffer * buffer, unsigned long value) +{ + 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 (nr_available_slots(cpu_buf) < 3) { + cpu_buf->sample_lost_overflow++; + 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; + add_code(cpu_buf, is_kernel); + } + + /* notice a task switch */ + if (cpu_buf->last_task != task) { + cpu_buf->last_task = task; + add_code(cpu_buf, (unsigned long)task); + } + + add_sample(cpu_buf, pc, event); + return 1; +} + +static int oprofile_begin_trace(struct oprofile_cpu_buffer * cpu_buf) +{ + if (nr_available_slots(cpu_buf) < 4) { + cpu_buf->sample_lost_overflow++; + return 0; + } + + 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; +} + + +void oprofile_add_sample(struct pt_regs * const regs, unsigned long event) +{ + struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()]; + unsigned long pc = profile_pc(regs); + int is_kernel = !user_mode(regs); + + if (!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, backtrace_depth); + oprofile_end_trace(cpu_buf); +} + + +void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event) +{ + struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()]; + log_sample(cpu_buf, pc, is_kernel, event); +} + + +void oprofile_add_trace(unsigned long pc) +{ + struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()]; + + if (!cpu_buf->tracing) + return; + + if (nr_available_slots(cpu_buf) < 1) { + cpu_buf->tracing = 0; + cpu_buf->sample_lost_overflow++; + 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) { + cpu_buf->tracing = 0; + cpu_buf->backtrace_aborted++; + return; + } + + add_sample(cpu_buf, pc, 0); +} + + + +/* + * 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(void * data) +{ + struct oprofile_cpu_buffer * b = data; + if (b->cpu != smp_processor_id()) { + printk("WQ on CPU%d, prefer CPU%d\n", + smp_processor_id(), b->cpu); + } + 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); +} |