This patch adds context switch tracing, of the format of:
_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
swapper-0 1d..3 137us+: 0:140:R --> 2912:120
sshd-2912 1d..3 216us+: 2912:120:S --> 0:140
swapper-0 1d..3 261us+: 0:140:R --> 2912:120
bash-2920 0d..3 267us+: 2920:120:S --> 0:140
sshd-2912 1d..3 330us!: 2912:120:S --> 0:140
swapper-0 1d..3 2389us+: 0:140:R --> 2847:120
yum-upda-2847 1d..3 2411us!: 2847:120:S --> 0:140
swapper-0 0d..3 11089us+: 0:140:R --> 3139:120
gdm-bina-3139 0d..3 11113us!: 3139:120:S --> 0:140
swapper-0 1d..3 102328us+: 0:140:R --> 2847:120
yum-upda-2847 1d..3 102348us!: 2847:120:S --> 0:140
Two files are added to /debugfs/tracing
sched_trace - outputs the above format.
sched_trace_ctrl
0 - turns off context switch tracing.
1 - turns on context switch tracing.
Signed-off-by: Steven Rostedt <[EMAIL PROTECTED]>
Cc: Mathieu Desnoyers <[EMAIL PROTECTED]>
---
lib/tracing/Kconfig | 10 +
lib/tracing/Makefile | 1
lib/tracing/trace_sched_switch.c | 205 +++++++++++++++++++++++++++++++++++++++
lib/tracing/tracer.c | 32 ++++++
lib/tracing/tracer.h | 18 +++
5 files changed, 265 insertions(+), 1 deletion(-)
Index: linux-mcount.git/lib/tracing/Kconfig
===================================================================
--- linux-mcount.git.orig/lib/tracing/Kconfig 2008-01-21 09:59:15.000000000
-0500
+++ linux-mcount.git/lib/tracing/Kconfig 2008-01-21 10:03:57.000000000
-0500
@@ -24,3 +24,13 @@ config FUNCTION_TRACER
insert a call to an architecture specific __mcount routine,
that the debugging mechanism using this facility will hook by
providing a set of inline routines.
+
+config CONTEXT_SWITCH_TRACER
+ bool "Trace process context switches"
+ depends on DEBUG_KERNEL
+ default n
+ select TRACING
+ help
+ This tracer hooks into the context switch and records
+ all switching of tasks.
+
Index: linux-mcount.git/lib/tracing/Makefile
===================================================================
--- linux-mcount.git.orig/lib/tracing/Makefile 2008-01-21 09:59:15.000000000
-0500
+++ linux-mcount.git/lib/tracing/Makefile 2008-01-21 10:03:57.000000000
-0500
@@ -1,6 +1,7 @@
obj-$(CONFIG_MCOUNT) += libmcount.o
obj-$(CONFIG_TRACING) += tracer.o
+obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
obj-$(CONFIG_FUNCTION_TRACER) += trace_function.o
libmcount-y := mcount.o
Index: linux-mcount.git/lib/tracing/trace_sched_switch.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-mcount.git/lib/tracing/trace_sched_switch.c 2008-01-21
10:03:57.000000000 -0500
@@ -0,0 +1,205 @@
+/*
+ * trace context switch
+ *
+ * Copyright (C) 2007 Steven Rostedt <[EMAIL PROTECTED]>
+ *
+ */
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/marker.h>
+#include <linux/mcount.h>
+
+#include "tracer.h"
+
+static struct tracing_trace sched_switch_trace __read_mostly;
+static DEFINE_PER_CPU(struct tracing_trace_cpu, sched_switch_trace_cpu);
+
+static int trace_enabled __read_mostly;
+static unsigned long trace_nr_entries = (16384UL);
+
+static int __init set_nr_entries(char *str)
+{
+ if (!str)
+ return 0;
+ trace_nr_entries = simple_strtoul(str, &str, 0);
+ return 1;
+}
+__setup("trace_ctx_entries=", set_nr_entries);
+
+static notrace void sched_switch_callback(const struct marker *mdata,
+ void *private_data,
+ const char *format, ...)
+{
+ struct tracing_trace *tr = mdata->private;
+ struct tracing_trace_cpu *data;
+ struct task_struct *prev;
+ struct task_struct *next;
+ unsigned long flags;
+ va_list ap;
+ int cpu;
+
+ if (likely(!trace_enabled))
+ return;
+
+ va_start(ap, format);
+ prev = va_arg(ap, typeof(prev));
+ next = va_arg(ap, typeof(next));
+ va_end(ap);
+
+ raw_local_irq_save(flags);
+ cpu = raw_smp_processor_id();
+ data = tr->data[cpu];
+ atomic_inc(&data->disabled);
+
+ if (likely(atomic_read(&data->disabled) == 1))
+ tracing_sched_switch_trace(tr, data, prev, next, flags);
+
+ atomic_dec(&data->disabled);
+ raw_local_irq_restore(flags);
+}
+
+static notrace void sched_switch_reset(struct tracing_trace *tr)
+{
+ int cpu;
+
+ tr->time_start = now();
+
+ for_each_online_cpu(cpu)
+ tracing_reset(tr->data[cpu]);
+}
+
+#ifdef CONFIG_DEBUG_FS
+static void sched_switch_trace_ctrl_update(struct tracing_trace *tr,
+ unsigned long val)
+{
+ val = !!val;
+
+ /* When starting a new trace, reset the buffers */
+ if (val)
+ sched_switch_reset(tr);
+
+ if (tr->ctrl ^ val) {
+ if (val)
+ trace_enabled = 1;
+ else
+ trace_enabled = 0;
+ tr->ctrl = val;
+ }
+}
+
+static __init void sched_switch_trace_init_debugfs(void)
+{
+ struct dentry *d_tracer;
+ struct dentry *entry;
+
+ d_tracer = tracing_init_dentry();
+
+ sched_switch_trace.ctrl_update = sched_switch_trace_ctrl_update;
+
+ entry = debugfs_create_file("sched_trace_ctrl", 0644, d_tracer,
+ &sched_switch_trace, &tracing_ctrl_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs "
+ "'sched_trace_ctrl' entry\n");
+
+ entry = debugfs_create_file("sched_trace", 0444, d_tracer,
+ &sched_switch_trace, &tracing_lt_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs 'sched_trace' entry\n");
+}
+
+#else
+static __init void sched_switch_trace_init_debugfs(void)
+{
+ /*
+ * No way to turn on or off the trace function
+ * without debugfs, so we just turn it on.
+ */
+}
+#endif
+
+static void sched_switch_trace_open(struct tracing_iterator *iter)
+{
+ /* stop the trace while dumping */
+ if (iter->tr->ctrl)
+ trace_enabled = 0;
+}
+
+static void sched_switch_trace_close(struct tracing_iterator *iter)
+{
+ if (iter->tr->ctrl)
+ trace_enabled = 1;
+}
+
+__init static int sched_switch_trace_alloc_buffers(void)
+{
+ const int order = page_order(trace_nr_entries * TRACING_ENTRY_SIZE);
+ const unsigned long size = (1UL << order) << PAGE_SHIFT;
+ struct tracing_entry *array;
+ int ret;
+ int i;
+
+ for_each_possible_cpu(i) {
+ sched_switch_trace.data[i] =
+ &per_cpu(sched_switch_trace_cpu, i);
+ array = (struct tracing_entry *)
+ __get_free_pages(GFP_KERNEL, order);
+ if (array == NULL) {
+ printk(KERN_ERR "sched_switch tracer: failed to"
+ " allocate %ld bytes for trace buffer!\n", size);
+ goto free_buffers;
+ }
+ sched_switch_trace.data[i]->trace = array;
+ }
+
+ /*
+ * Since we allocate by orders of pages, we may be able to
+ * round up a bit.
+ */
+ sched_switch_trace.entries = size / TRACING_ENTRY_SIZE;
+
+ pr_info("sched_switch tracer: %ld bytes allocated for %ld",
+ size, trace_nr_entries);
+ pr_info(" entries of %ld bytes\n", (long)TRACING_ENTRY_SIZE);
+ pr_info(" actual entries %ld\n", sched_switch_trace.entries);
+
+ sched_switch_trace_init_debugfs();
+
+ sched_switch_trace.open = sched_switch_trace_open;
+ sched_switch_trace.close = sched_switch_trace_close;
+
+ ret = marker_probe_register("kernel_sched_schedule",
+ "prev %p next %p",
+ sched_switch_callback,
+ &sched_switch_trace);
+ if (ret) {
+ pr_info("sched trace: Couldn't add marker"
+ " probe to switch_to\n");
+ goto out;
+ }
+
+ ret = marker_arm("kernel_sched_schedule");
+ if (ret) {
+ pr_info("sched trace: Couldn't arm probe switch_to\n");
+ goto out;
+ }
+
+ out:
+ return 0;
+
+ free_buffers:
+ for (i-- ; i >= 0; i--) {
+ struct tracing_trace_cpu *data = sched_switch_trace.data[i];
+
+ if (data && data->trace) {
+ free_pages((unsigned long)data->trace, order);
+ data->trace = NULL;
+ }
+ }
+ return -ENOMEM;
+}
+
+device_initcall(sched_switch_trace_alloc_buffers);
Index: linux-mcount.git/lib/tracing/tracer.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.c 2008-01-21 10:01:49.000000000
-0500
+++ linux-mcount.git/lib/tracing/tracer.c 2008-01-21 10:03:57.000000000
-0500
@@ -31,6 +31,7 @@ enum trace_type {
__TRACE_FIRST_TYPE = 0,
TRACE_FN,
+ TRACE_CTX,
__TRACE_LAST_TYPE
};
@@ -107,6 +108,24 @@ notrace void tracing_function_trace(stru
entry->fn.parent_ip = parent_ip;
}
+notrace void tracing_sched_switch_trace(struct tracing_trace *tr,
+ struct tracing_trace_cpu *data,
+ struct task_struct *prev,
+ struct task_struct *next,
+ unsigned long flags)
+{
+ struct tracing_entry *entry;
+
+ entry = tracing_get_trace_entry(tr, data);
+ tracing_generic_entry_update(entry, flags);
+ entry->type = TRACE_CTX;
+ entry->ctx.prev_pid = prev->pid;
+ entry->ctx.prev_prio = prev->prio;
+ entry->ctx.prev_state = prev->state;
+ entry->ctx.next_pid = next->pid;
+ entry->ctx.next_prio = next->prio;
+}
+
#ifdef CONFIG_DEBUG_FS
enum trace_iterator {
TRACE_ITER_SYM_ONLY = 1,
@@ -414,6 +433,8 @@ lat_print_timestamp(struct seq_file *m,
seq_puts(m, " : ");
}
+static const char state_to_char[] = TASK_STATE_TO_CHAR_STR;
+
static void notrace
print_lat_fmt(struct seq_file *m, struct tracing_iterator *iter,
unsigned int trace_idx, int cpu)
@@ -424,6 +445,7 @@ print_lat_fmt(struct seq_file *m, struct
unsigned long rel_usecs;
int sym_only = !!(trace_flags & TRACE_ITER_SYM_ONLY);
int verbose = !!(trace_flags & TRACE_ITER_VERBOSE);
+ int S;
if (!next_entry)
next_entry = entry;
@@ -450,6 +472,16 @@ print_lat_fmt(struct seq_file *m, struct
seq_print_ip_sym(m, entry->fn.parent_ip, sym_only);
seq_puts(m, ")\n");
break;
+ case TRACE_CTX:
+ S = entry->ctx.prev_state < sizeof(state_to_char) ?
+ state_to_char[entry->ctx.prev_state] : 'X';
+ seq_printf(m, " %d:%d:%c --> %d:%d\n",
+ entry->ctx.prev_pid,
+ entry->ctx.prev_prio,
+ S,
+ entry->ctx.next_pid,
+ entry->ctx.next_prio);
+ break;
}
}
Index: linux-mcount.git/lib/tracing/tracer.h
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.h 2008-01-21 09:59:15.000000000
-0500
+++ linux-mcount.git/lib/tracing/tracer.h 2008-01-21 10:03:57.000000000
-0500
@@ -10,6 +10,14 @@ struct tracing_function {
unsigned long parent_ip;
};
+struct tracing_sched_switch {
+ unsigned int prev_pid;
+ unsigned char prev_prio;
+ unsigned char prev_state;
+ unsigned int next_pid;
+ unsigned char next_prio;
+};
+
struct tracing_entry {
char type;
char cpu; /* who will want to trace more than 256 CPUS? */
@@ -18,7 +26,10 @@ struct tracing_entry {
int pid;
cycle_t t;
char comm[TASK_COMM_LEN];
- struct tracing_function fn;
+ union {
+ struct tracing_function fn;
+ struct tracing_sched_switch ctx;
+ };
};
struct tracing_trace_cpu {
@@ -75,6 +86,11 @@ void tracing_function_trace(struct traci
unsigned long ip,
unsigned long parent_ip,
unsigned long flags);
+void tracing_sched_switch_trace(struct tracing_trace *tr,
+ struct tracing_trace_cpu *data,
+ struct task_struct *prev,
+ struct task_struct *next,
+ unsigned long flags);
extern struct file_operations tracing_fops;
extern struct file_operations tracing_lt_fops;
--
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