The situation around sched_info is somewhat complicated, it is used by
sched_stats and delayacct and, indirectly, kvm.
If SCHEDSTATS=Y (but disabled by default) sched_info_on() is
unconditionally true -- this is the case for all distro kernel configs
I checked.
If for some reason SCHEDSTATS=N, but TASK_DELAY_ACCT=Y, then
sched_info_on() can return false when delayacct is disabled,
presumably because there would be no other users left; except kvm is.
Instead of complicating matters further by accurately accounting
sched_stat and kvm state, simply unconditionally enable when
SCHED_INFO=Y, matching the common distro case.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
include/linux/sched/stat.h | 10 ++--------
kernel/delayacct.c | 1 -
kernel/sched/stats.h | 37 ++++++++++---------------------------
3 files changed, 12 insertions(+), 36 deletions(-)
--- a/include/linux/sched/stat.h
+++ b/include/linux/sched/stat.h
@@ -3,6 +3,7 @@
#define _LINUX_SCHED_STAT_H
#include <linux/percpu.h>
+#include <linux/kconfig.h>
/*
* Various counters maintained by the scheduler and fork(),
@@ -23,14 +24,7 @@ extern unsigned long nr_iowait_cpu(int c
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
+ return IS_ENABLED(CONFIG_SCHED_INFO);
}
#ifdef CONFIG_SCHEDSTATS
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -15,7 +15,6 @@
#include <linux/module.h>
int delayacct_on __read_mostly = 1; /* Delay accounting turned on/off */
-EXPORT_SYMBOL_GPL(delayacct_on);
struct kmem_cache *delayacct_cache;
static int __init delayacct_setup_disable(char *str)
--- a/kernel/sched/stats.h
+++ b/kernel/sched/stats.h
@@ -150,11 +150,6 @@ static inline void psi_sched_switch(stru
#endif /* CONFIG_PSI */
#ifdef CONFIG_SCHED_INFO
-static inline void sched_info_reset_dequeued(struct task_struct *t)
-{
- t->sched_info.last_queued = 0;
-}
-
/*
* We are interested in knowing how long it was from the *first* time a
* task was queued to the time that it finally hit a CPU, we call this routine
@@ -163,13 +158,12 @@ static inline void sched_info_reset_dequ
*/
static inline void sched_info_dequeue(struct rq *rq, struct task_struct *t)
{
- unsigned long long now = rq_clock(rq), delta = 0;
+ unsigned long long delta = 0;
- if (sched_info_on()) {
- if (t->sched_info.last_queued)
- delta = now - t->sched_info.last_queued;
+ if (t->sched_info.last_queued) {
+ delta = rq_clock(rq) - t->sched_info.last_queued;
+ t->sched_info.last_queued = 0;
}
- sched_info_reset_dequeued(t);
t->sched_info.run_delay += delta;
rq_sched_info_dequeue(rq, delta);
@@ -184,9 +178,10 @@ static void sched_info_arrive(struct rq
{
unsigned long long now = rq_clock(rq), delta = 0;
- if (t->sched_info.last_queued)
+ if (t->sched_info.last_queued) {
delta = now - t->sched_info.last_queued;
- sched_info_reset_dequeued(t);
+ t->sched_info.last_queued = 0;
+ }
t->sched_info.run_delay += delta;
t->sched_info.last_arrival = now;
t->sched_info.pcount++;
@@ -201,10 +196,8 @@ static void sched_info_arrive(struct rq
*/
static inline void sched_info_enqueue(struct rq *rq, struct task_struct *t)
{
- if (sched_info_on()) {
- if (!t->sched_info.last_queued)
- t->sched_info.last_queued = rq_clock(rq);
- }
+ if (!t->sched_info.last_queued)
+ t->sched_info.last_queued = rq_clock(rq);
}
/*
@@ -231,7 +224,7 @@ static inline void sched_info_depart(str
* the idle task.) We are only called when prev != next.
*/
static inline void
-__sched_info_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next)
+sched_info_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next)
{
/*
* prev now departs the CPU. It's not interesting to record
@@ -245,18 +238,8 @@ __sched_info_switch(struct rq *rq, struc
sched_info_arrive(rq, next);
}
-static inline void
-sched_info_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next)
-{
- if (sched_info_on())
- __sched_info_switch(rq, prev, next);
-}
-
#else /* !CONFIG_SCHED_INFO: */
# define sched_info_enqueue(rq, t) do { } while (0)
-# define sched_info_reset_dequeued(t) do { } while (0)
# define sched_info_dequeue(rq, t) do { } while (0)
-# define sched_info_depart(rq, t) do { } while (0)
-# define sched_info_arrive(rq, next) do { } while (0)
# define sched_info_switch(rq, t, next) do { } while (0)
#endif /* CONFIG_SCHED_INFO */
