Assuming this stuff isn't actually used much; disable it by default
and avoid allocating and tracking the task_delay_info structure.
taskstats is changed to still report the regular sched and sched_info
and only skip the missing task_delay_info fields instead of not
reporting anything.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
Documentation/accounting/delay-accounting.rst | 8 ++++----
Documentation/admin-guide/kernel-parameters.txt | 2 +-
include/linux/delayacct.h | 16 ++++------------
kernel/delayacct.c | 19 +++++++++++--------
4 files changed, 20 insertions(+), 25 deletions(-)
--- a/Documentation/accounting/delay-accounting.rst
+++ b/Documentation/accounting/delay-accounting.rst
@@ -69,13 +69,13 @@ Usage
CONFIG_TASK_DELAY_ACCT=y
CONFIG_TASKSTATS=y
-Delay accounting is enabled by default at boot up.
-To disable, add::
+Delay accounting is disabled by default at boot up.
+To enable, add::
- nodelayacct
+ delayacct
to the kernel boot options. The rest of the instructions
-below assume this has not been done.
+below assume this has been done.
After the system has booted up, use a utility
similar to getdelays.c to access the delays
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3213,7 +3213,7 @@
noclflush [BUGS=X86] Don't use the CLFLUSH instruction
- nodelayacct [KNL] Disable per-task delay accounting
+ delayacct [KNL] Enable per-task delay accounting
nodsp [SH] Disable hardware DSP at boot time.
--- a/include/linux/delayacct.h
+++ b/include/linux/delayacct.h
@@ -61,7 +61,7 @@ struct task_delay_info {
#include <linux/jump_label.h>
#ifdef CONFIG_TASK_DELAY_ACCT
-DECLARE_STATIC_KEY_TRUE(delayacct_key);
+DECLARE_STATIC_KEY_FALSE(delayacct_key);
extern int delayacct_on; /* Delay accounting turned on/off */
extern struct kmem_cache *delayacct_cache;
extern void delayacct_init(void);
@@ -69,7 +69,7 @@ extern void __delayacct_tsk_init(struct
extern void __delayacct_tsk_exit(struct task_struct *);
extern void __delayacct_blkio_start(void);
extern void __delayacct_blkio_end(struct task_struct *);
-extern int __delayacct_add_tsk(struct taskstats *, struct task_struct *);
+extern int delayacct_add_tsk(struct taskstats *, struct task_struct *);
extern __u64 __delayacct_blkio_ticks(struct task_struct *);
extern void __delayacct_freepages_start(void);
extern void __delayacct_freepages_end(void);
@@ -116,7 +116,7 @@ static inline void delayacct_tsk_free(st
static inline void delayacct_blkio_start(void)
{
- if (!static_branch_likely(&delayacct_key))
+ if (!static_branch_unlikely(&delayacct_key))
return;
delayacct_set_flag(DELAYACCT_PF_BLKIO);
@@ -126,7 +126,7 @@ static inline void delayacct_blkio_start
static inline void delayacct_blkio_end(struct task_struct *p)
{
- if (!static_branch_likely(&delayacct_key))
+ if (!static_branch_unlikely(&delayacct_key))
return;
if (p->delays)
@@ -134,14 +134,6 @@ static inline void delayacct_blkio_end(s
delayacct_clear_flag(DELAYACCT_PF_BLKIO);
}
-static inline int delayacct_add_tsk(struct taskstats *d,
- struct task_struct *tsk)
-{
- if (!delayacct_on || !tsk->delays)
- return 0;
- return __delayacct_add_tsk(d, tsk);
-}
-
static inline __u64 delayacct_blkio_ticks(struct task_struct *tsk)
{
if (tsk->delays)
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -14,23 +14,23 @@
#include <linux/delayacct.h>
#include <linux/module.h>
-DEFINE_STATIC_KEY_TRUE(delayacct_key);
-int delayacct_on __read_mostly = 1; /* Delay accounting turned on/off */
+DEFINE_STATIC_KEY_FALSE(delayacct_key);
+int delayacct_on __read_mostly; /* Delay accounting turned on/off */
struct kmem_cache *delayacct_cache;
-static int __init delayacct_setup_disable(char *str)
+static int __init delayacct_setup_enable(char *str)
{
- delayacct_on = 0;
+ delayacct_on = 1;
return 1;
}
-__setup("nodelayacct", delayacct_setup_disable);
+__setup("delayacct", delayacct_setup_enable);
void delayacct_init(void)
{
delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC|SLAB_ACCOUNT);
delayacct_tsk_init(&init_task);
- if (!delayacct_on)
- static_branch_disable(&delayacct_key);
+ if (delayacct_on)
+ static_branch_enable(&delayacct_key);
}
void __delayacct_tsk_init(struct task_struct *tsk)
@@ -83,7 +83,7 @@ void __delayacct_blkio_end(struct task_s
delayacct_end(&delays->lock, &delays->blkio_start, total, count);
}
-int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
+int delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
{
u64 utime, stime, stimescaled, utimescaled;
unsigned long long t2, t3;
@@ -118,6 +118,9 @@ int __delayacct_add_tsk(struct taskstats
d->cpu_run_virtual_total =
(tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
+ if (!tsk->delays)
+ return 0;
+
/* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
raw_spin_lock_irqsave(&tsk->delays->lock, flags);
