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Subject[Patch 3/8] cpu delay collection via schedstats
Changelog

Fixes comments by akpm
- comments about locking used in rq_sched_info_arrive/depart

No fix needed/possible
- redundant extern declaration of delayacct_on in sched.h
suggested location (delayacct.h) cannot be used as it includes sched.h
extern declaration moved to where its needed
- move unlikely declaration inside sched_info_on
Function only returns constants. Cannot be done.
- removal of #if defined in sched_fork (Dave Hansen)
Refactoring suggested does not work if only SCHEDSTATS is configured

delayacct-shedstats.patch

Make the task-related schedstats functions
callable by delay accounting even if schedstats
collection isn't turned on. This removes the
dependency of delay accounting on schedstats.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>

include/linux/sched.h | 21 +++++++++++++++---
kernel/sched.c | 56 ++++++++++++++++++++++++++++++++++----------------
2 files changed, 56 insertions(+), 21 deletions(-)
Index: linux-2.6.17-rc1/include/linux/sched.h
===================================================================
--- linux-2.6.17-rc1.orig/include/linux/sched.h 2006-04-21 20:29:13.000000000 -0400
+++ linux-2.6.17-rc1/include/linux/sched.h 2006-04-21 20:29:15.000000000 -0400
@@ -521,7 +521,7 @@ typedef struct prio_array prio_array_t;
struct backing_dev_info;
struct reclaim_state;

-#ifdef CONFIG_SCHEDSTATS
+#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
struct sched_info {
/* cumulative counters */
unsigned long cpu_time, /* time spent on the cpu */
@@ -532,9 +532,11 @@ struct sched_info {
unsigned long last_arrival, /* when we last ran on a cpu */
last_queued; /* when we were last queued to run */
};
+#endif /* defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT) */

+#ifdef CONFIG_SCHEDSTATS
extern struct file_operations proc_schedstat_operations;
-#endif
+#endif /* CONFIG_SCHEDSTATS */

#ifdef CONFIG_TASK_DELAY_ACCT
struct task_delay_info {
@@ -557,8 +559,19 @@ struct task_delay_info {
u32 blkio_count;
u32 swapin_count;
};
-#endif
+#endif /* CONFIG_TASK_DELAY_ACCT */

+static inline int sched_info_on(void)
+{
+#ifdef CONFIG_SCHEDSTATS
+ return 1;
+#elif defined(CONFIG_TASK_DELAY_ACCT)
+ extern int delayacct_on;
+ return delayacct_on;
+#else
+ return 0;
+#endif
+}

enum idle_type
{
@@ -744,7 +757,7 @@ struct task_struct {
cpumask_t cpus_allowed;
unsigned int time_slice, first_time_slice;

-#ifdef CONFIG_SCHEDSTATS
+#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
struct sched_info sched_info;
#endif

Index: linux-2.6.17-rc1/kernel/sched.c
===================================================================
--- linux-2.6.17-rc1.orig/kernel/sched.c 2006-04-21 20:29:13.000000000 -0400
+++ linux-2.6.17-rc1/kernel/sched.c 2006-04-21 20:29:15.000000000 -0400
@@ -469,9 +469,32 @@ struct file_operations proc_schedstat_op
.release = single_release,
};

+/*
+ * Expects runqueue lock to be held for atomicity of update
+ */
+static inline void rq_sched_info_arrive(struct runqueue *rq,
+ unsigned long diff)
+{
+ if (rq) {
+ rq->rq_sched_info.run_delay += diff;
+ rq->rq_sched_info.pcnt++;
+ }
+}
+
+/*
+ * Expects runqueue lock to be held for atomicity of update
+ */
+static inline void rq_sched_info_depart(struct runqueue *rq,
+ unsigned long diff)
+{
+ if (rq)
+ rq->rq_sched_info.cpu_time += diff;
+}
# define schedstat_inc(rq, field) do { (rq)->field++; } while (0)
# define schedstat_add(rq, field, amt) do { (rq)->field += (amt); } while (0)
#else /* !CONFIG_SCHEDSTATS */
+static inline void rq_sched_info_arrive(struct runqueue *rq, unsigned long diff) {}
+static inline void rq_sched_info_depart(struct runqueue *rq, unsigned long diff) {}
# define schedstat_inc(rq, field) do { } while (0)
# define schedstat_add(rq, field, amt) do { } while (0)
#endif
@@ -491,7 +514,7 @@ static inline runqueue_t *this_rq_lock(v
return rq;
}

-#ifdef CONFIG_SCHEDSTATS
+#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
/*
* Called when a process is dequeued from the active array and given
* the cpu. We should note that with the exception of interactive
@@ -520,7 +543,6 @@ static inline void sched_info_dequeued(t
static void sched_info_arrive(task_t *t)
{
unsigned long now = jiffies, diff = 0;
- struct runqueue *rq = task_rq(t);

if (t->sched_info.last_queued)
diff = now - t->sched_info.last_queued;
@@ -529,11 +551,7 @@ static void sched_info_arrive(task_t *t)
t->sched_info.last_arrival = now;
t->sched_info.pcnt++;

- if (!rq)
- return;
-
- rq->rq_sched_info.run_delay += diff;
- rq->rq_sched_info.pcnt++;
+ rq_sched_info_arrive(task_rq(t), diff);
}

/*
@@ -553,8 +571,9 @@ static void sched_info_arrive(task_t *t)
*/
static inline void sched_info_queued(task_t *t)
{
- if (!t->sched_info.last_queued)
- t->sched_info.last_queued = jiffies;
+ if (unlikely(sched_info_on()))
+ if (!t->sched_info.last_queued)
+ t->sched_info.last_queued = jiffies;
}

/*
@@ -563,13 +582,10 @@ static inline void sched_info_queued(tas
*/
static inline void sched_info_depart(task_t *t)
{
- struct runqueue *rq = task_rq(t);
unsigned long diff = jiffies - t->sched_info.last_arrival;

t->sched_info.cpu_time += diff;
-
- if (rq)
- rq->rq_sched_info.cpu_time += diff;
+ rq_sched_info_depart(task_rq(t), diff);
}

/*
@@ -577,7 +593,7 @@ static inline void sched_info_depart(tas
* their time slice. (This may also be called when switching to or from
* the idle task.) We are only called when prev != next.
*/
-static inline void sched_info_switch(task_t *prev, task_t *next)
+static inline void __sched_info_switch(task_t *prev, task_t *next)
{
struct runqueue *rq = task_rq(prev);

@@ -592,10 +608,15 @@ static inline void sched_info_switch(tas
if (next != rq->idle)
sched_info_arrive(next);
}
+static inline void sched_info_switch(task_t *prev, task_t *next)
+{
+ if (unlikely(sched_info_on()))
+ __sched_info_switch(prev, next);
+}
#else
#define sched_info_queued(t) do { } while (0)
#define sched_info_switch(t, next) do { } while (0)
-#endif /* CONFIG_SCHEDSTATS */
+#endif /* CONFIG_SCHEDSTATS || CONFIG_TASK_DELAY_ACCT */

/*
* Adding/removing a task to/from a priority array:
@@ -1351,8 +1372,9 @@ void fastcall sched_fork(task_t *p, int
p->state = TASK_RUNNING;
INIT_LIST_HEAD(&p->run_list);
p->array = NULL;
-#ifdef CONFIG_SCHEDSTATS
- memset(&p->sched_info, 0, sizeof(p->sched_info));
+#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
+ if (unlikely(sched_info_on()))
+ memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
p->oncpu = 0;
-
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