Add schedule tracing support

This patch introduces the sched_trace infrastructure, which in
principle allows tracing the generated schedule.  However, this patch
does not yet integrate the callbacks with the kernel.

3 files changed, 278 insertions, 0 deletions

diff --git a/litmus/Kconfig b/litmus/Kconfig
index e4624ee20adc..19211ac1320a 100644
--- a/litmus/Kconfig
+++ b/litmus/Kconfig
@@ -24,6 +24,40 @@ config FEATHER_TRACE
           you still need to enable SCHED_TASK_TRACE and/or SCHED_OVERHEAD_TRACE to
           actually enable any events.
 
+config SCHED_TASK_TRACE
+        bool "Trace real-time tasks"
+        depends on FEATHER_TRACE
+        default y
+        help
+          Include support for the sched_trace_XXX() tracing functions. This
+          allows the collection of real-time task events such as job
+          completions, job releases, early completions, etc. This results in  a
+          small overhead in the scheduling code. Disable if the overhead is not
+          acceptable (e.g., benchmarking).
+
+          Say Yes for debugging.
+          Say No for overhead tracing.
+
+config SCHED_TASK_TRACE_SHIFT
+       int "Buffer size for sched_trace_xxx() events"
+       depends on SCHED_TASK_TRACE
+       range 8 13
+       default 9
+       help
+
+         Select the buffer size of sched_trace_xxx() events as a power of two.
+         These buffers are statically allocated as per-CPU data. Each event
+         requires 24 bytes storage plus one additional flag byte. Too large
+         buffers can cause issues with the per-cpu allocator (and waste
+         memory). Too small buffers can cause scheduling events to be lost. The
+         "right" size is workload dependent and depends on the number of tasks,
+         each task's period, each task's number of suspensions, and how often
+         the buffer is flushed.
+
+         Examples: 12 =>   4k events
+                   10 =>   1k events
+                    8 =>  512 events
+
 config SCHED_OVERHEAD_TRACE
         bool "Record timestamps for overhead measurements"
         depends on FEATHER_TRACE
diff --git a/litmus/Makefile b/litmus/Makefile
index 07f065f9748f..6318f1c6fac8 100644
--- a/litmus/Makefile
+++ b/litmus/Makefile
@@ -3,5 +3,6 @@
 #
 
 obj-$(CONFIG_FEATHER_TRACE) += ft_event.o ftdev.o
+obj-$(CONFIG_SCHED_TASK_TRACE) += sched_task_trace.o
 obj-$(CONFIG_SCHED_DEBUG_TRACE) += sched_trace.o
 obj-$(CONFIG_SCHED_OVERHEAD_TRACE) += trace.o
diff --git a/litmus/sched_task_trace.c b/litmus/sched_task_trace.c
new file mode 100644
index 000000000000..4f95551df1b4
--- /dev/null
+++ b/litmus/sched_task_trace.c
@@ -0,0 +1,243 @@
+/*
+ * sched_task_trace.c -- record scheduling events to a byte stream
+ */
+
+#define NO_TASK_TRACE_DECLS
+
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/percpu.h>
+
+#include <litmus/ftdev.h>
+#include <litmus/litmus.h>
+
+#include <litmus/sched_trace.h>
+#include <litmus/feather_trace.h>
+#include <litmus/ftdev.h>
+
+
+#define NO_EVENTS               (1 << CONFIG_SCHED_TASK_TRACE_SHIFT)
+
+#define now() litmus_clock()
+
+struct local_buffer {
+        struct st_event_record record[NO_EVENTS];
+        char   flag[NO_EVENTS];
+        struct ft_buffer ftbuf;
+};
+
+DEFINE_PER_CPU(struct local_buffer, st_event_buffer);
+
+static struct ftdev st_dev;
+
+static int st_dev_can_open(struct ftdev *dev, unsigned int cpu)
+{
+        return cpu_online(cpu) ? 0 : -ENODEV;
+}
+
+static int __init init_sched_task_trace(void)
+{
+        struct local_buffer* buf;
+        int i, ok = 0, err;
+        printk("Allocated %u sched_trace_xxx() events per CPU "
+               "(buffer size: %d bytes)\n",
+               NO_EVENTS, (int) sizeof(struct local_buffer));
+
+        err = ftdev_init(&st_dev, THIS_MODULE,
+                        num_online_cpus(), "sched_trace");
+        if (err)
+                goto err_out;
+
+        for (i = 0; i < st_dev.minor_cnt; i++) {
+                buf = &per_cpu(st_event_buffer, i);
+                ok += init_ft_buffer(&buf->ftbuf, NO_EVENTS,
+                                     sizeof(struct st_event_record),
+                                     buf->flag,
+                                     buf->record);
+                st_dev.minor[i].buf = &buf->ftbuf;
+        }
+        if (ok == st_dev.minor_cnt) {
+                st_dev.can_open = st_dev_can_open;
+                err = register_ftdev(&st_dev);
+                if (err)
+                        goto err_dealloc;
+        } else {
+                err = -EINVAL;
+                goto err_dealloc;
+        }
+
+        return 0;
+
+err_dealloc:
+        ftdev_exit(&st_dev);
+err_out:
+        printk(KERN_WARNING "Could not register sched_trace module\n");
+        return err;
+}
+
+static void __exit exit_sched_task_trace(void)
+{
+        ftdev_exit(&st_dev);
+}
+
+module_init(init_sched_task_trace);
+module_exit(exit_sched_task_trace);
+
+
+static inline struct st_event_record* get_record(u8 type, struct task_struct* t)
+{
+        struct st_event_record* rec = NULL;
+        struct local_buffer* buf;
+
+        buf = &get_cpu_var(st_event_buffer);
+        if (ft_buffer_start_write(&buf->ftbuf, (void**) &rec)) {
+                rec->hdr.type = type;
+                rec->hdr.cpu  = smp_processor_id();
+                rec->hdr.pid  = t ? t->pid : 0;
+                rec->hdr.job  = t ? t->rt_param.job_params.job_no : 0;
+        } else {
+                put_cpu_var(st_event_buffer);
+        }
+        /* rec will be NULL if it failed */
+        return rec;
+}
+
+static inline void put_record(struct st_event_record* rec)
+{
+        struct local_buffer* buf;
+        /* don't use get_cpu_var() here, get_record() did that already for us */
+        buf = this_cpu_ptr(&st_event_buffer);
+        ft_buffer_finish_write(&buf->ftbuf, rec);
+        /* matches the get_cpu_var() in get_record() */
+        put_cpu_var(st_event_buffer);
+}
+
+feather_callback void do_sched_trace_task_name(unsigned long id, unsigned long _task)
+{
+        struct task_struct *t = (struct task_struct*) _task;
+        struct st_event_record* rec = get_record(ST_NAME, t);
+        int i;
+        if (rec) {
+                for (i = 0; i < min(TASK_COMM_LEN, ST_NAME_LEN); i++)
+                        rec->data.name.cmd[i] = t->comm[i];
+                put_record(rec);
+        }
+}
+
+feather_callback void do_sched_trace_task_param(unsigned long id, unsigned long _task)
+{
+        struct task_struct *t = (struct task_struct*) _task;
+        struct st_event_record* rec = get_record(ST_PARAM, t);
+        if (rec) {
+                rec->data.param.wcet      = get_exec_cost(t);
+                rec->data.param.period    = get_rt_period(t);
+                rec->data.param.phase     = get_rt_phase(t);
+                rec->data.param.partition = get_partition(t);
+                rec->data.param.class     = get_class(t);
+                put_record(rec);
+        }
+}
+
+feather_callback void do_sched_trace_task_release(unsigned long id, unsigned long _task)
+{
+        struct task_struct *t = (struct task_struct*) _task;
+        struct st_event_record* rec = get_record(ST_RELEASE, t);
+        if (rec) {
+                rec->data.release.release  = get_release(t);
+                rec->data.release.deadline = get_deadline(t);
+                put_record(rec);
+        }
+}
+
+/* skipped: st_assigned_data, we don't use it atm */
+
+feather_callback void do_sched_trace_task_switch_to(unsigned long id,
+                                                    unsigned long _task)
+{
+        struct task_struct *t = (struct task_struct*) _task;
+        struct st_event_record* rec;
+        if (is_realtime(t)) {
+                rec = get_record(ST_SWITCH_TO, t);
+                if (rec) {
+                        rec->data.switch_to.when      = now();
+                        rec->data.switch_to.exec_time = get_exec_time(t);
+                        put_record(rec);
+                }
+        }
+}
+
+feather_callback void do_sched_trace_task_switch_away(unsigned long id,
+                                                      unsigned long _task)
+{
+        struct task_struct *t = (struct task_struct*) _task;
+        struct st_event_record* rec;
+        if (is_realtime(t)) {
+                rec = get_record(ST_SWITCH_AWAY, t);
+                if (rec) {
+                        rec->data.switch_away.when      = now();
+                        rec->data.switch_away.exec_time = get_exec_time(t);
+                        put_record(rec);
+                }
+        }
+}
+
+feather_callback void do_sched_trace_task_completion(unsigned long id,
+                                                     unsigned long _task,
+                                                     unsigned long forced)
+{
+        struct task_struct *t = (struct task_struct*) _task;
+        struct st_event_record* rec = get_record(ST_COMPLETION, t);
+        if (rec) {
+                rec->data.completion.when   = now();
+                rec->data.completion.forced = forced;
+                put_record(rec);
+        }
+}
+
+feather_callback void do_sched_trace_task_block(unsigned long id,
+                                                unsigned long _task)
+{
+        struct task_struct *t = (struct task_struct*) _task;
+        struct st_event_record* rec = get_record(ST_BLOCK, t);
+        if (rec) {
+                rec->data.block.when      = now();
+                put_record(rec);
+        }
+}
+
+feather_callback void do_sched_trace_task_resume(unsigned long id,
+                                                 unsigned long _task)
+{
+        struct task_struct *t = (struct task_struct*) _task;
+        struct st_event_record* rec = get_record(ST_RESUME, t);
+        if (rec) {
+                rec->data.resume.when      = now();
+                put_record(rec);
+        }
+}
+
+feather_callback void do_sched_trace_sys_release(unsigned long id,
+                                                 unsigned long _start)
+{
+        lt_t *start = (lt_t*) _start;
+        struct st_event_record* rec = get_record(ST_SYS_RELEASE, NULL);
+        if (rec) {
+                rec->data.sys_release.when    = now();
+                rec->data.sys_release.release = *start;
+                put_record(rec);
+        }
+}
+
+feather_callback void do_sched_trace_action(unsigned long id,
+                                            unsigned long _task,
+                                            unsigned long action)
+{
+        struct task_struct *t = (struct task_struct*) _task;
+        struct st_event_record* rec = get_record(ST_ACTION, t);
+
+        if (rec) {
+                rec->data.action.when   = now();
+                rec->data.action.action = action;
+                put_record(rec);
+        }
+}