Just small clarifications and a tiny simplification.
Thanks.
Frederic Weisbecker (2):
hrtimer: Simplify get_target_base() returning current base
hrtimer: Unconfuse a bit switch_hrtimer_base
kernel/time/hrtimer.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
--
2.1.4
Instead of fetching again the current cpu base, just take it from the
parameter.
Signed-off-by: Frederic Weisbecker <[email protected]>
---
kernel/time/hrtimer.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 55575d4..f9eb21b 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -183,7 +183,7 @@ struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
int pinned)
{
if (pinned || !base->migration_enabled)
- return this_cpu_ptr(&hrtimer_bases);
+ return base;
return &per_cpu(hrtimer_bases, get_nohz_timer_target());
}
#else
@@ -191,7 +191,7 @@ static inline
struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
int pinned)
{
- return this_cpu_ptr(&hrtimer_bases);
+ return base;
}
#endif
--
2.1.4
The variable called "this_base" is confusing because its name suggests
it's of "struct hrtimer_clock_base" type, along with "base" and "new_base"
which doesn't help understanding this complicated function.
Make its name clearer and fix the misleading comments while at it.
Signed-off-by: Frederic Weisbecker <[email protected]>
---
kernel/time/hrtimer.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index f9eb21b..1828ed0 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -196,18 +196,20 @@ struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
#endif
/*
- * Switch the timer base to the current CPU when possible.
+ * Switch the timer base to a power-optimized selected CPU target.
+ * If that would involve clock reprogramming, which we can't do on a remote
+ * target, just switch to the current CPU.
*/
static inline struct hrtimer_clock_base *
switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
int pinned)
{
- struct hrtimer_cpu_base *new_cpu_base, *this_base;
+ struct hrtimer_cpu_base *new_cpu_base, *this_cpu_base;
struct hrtimer_clock_base *new_base;
int basenum = base->index;
- this_base = this_cpu_ptr(&hrtimer_bases);
- new_cpu_base = get_target_base(this_base, pinned);
+ this_cpu_base = this_cpu_ptr(&hrtimer_bases);
+ new_cpu_base = get_target_base(this_cpu_base, pinned);
again:
new_base = &new_cpu_base->clock_base[basenum];
@@ -229,19 +231,19 @@ again:
raw_spin_unlock(&base->cpu_base->lock);
raw_spin_lock(&new_base->cpu_base->lock);
- if (new_cpu_base != this_base &&
+ if (new_cpu_base != this_cpu_base &&
hrtimer_check_target(timer, new_base)) {
raw_spin_unlock(&new_base->cpu_base->lock);
raw_spin_lock(&base->cpu_base->lock);
- new_cpu_base = this_base;
+ new_cpu_base = this_cpu_base;
timer->base = base;
goto again;
}
timer->base = new_base;
} else {
- if (new_cpu_base != this_base &&
+ if (new_cpu_base != this_cpu_base &&
hrtimer_check_target(timer, new_base)) {
- new_cpu_base = this_base;
+ new_cpu_base = this_cpu_base;
goto again;
}
}
--
2.1.4
Commit-ID: 662b3e194656cc713d51d52780fb71f499c46619
Gitweb: http://git.kernel.org/tip/662b3e194656cc713d51d52780fb71f499c46619
Author: Frederic Weisbecker <[email protected]>
AuthorDate: Tue, 18 Aug 2015 16:18:28 +0200
Committer: Thomas Gleixner <[email protected]>
CommitDate: Tue, 18 Aug 2015 18:36:59 +0200
hrtimer: Simplify get_target_base() by returning current base
Instead of fetching again the current cpu base, just take it from the
parameter.
Signed-off-by: Frederic Weisbecker <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
---
kernel/time/hrtimer.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 55575d4..f9eb21b 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -183,7 +183,7 @@ struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
int pinned)
{
if (pinned || !base->migration_enabled)
- return this_cpu_ptr(&hrtimer_bases);
+ return base;
return &per_cpu(hrtimer_bases, get_nohz_timer_target());
}
#else
@@ -191,7 +191,7 @@ static inline
struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
int pinned)
{
- return this_cpu_ptr(&hrtimer_bases);
+ return base;
}
#endif
Commit-ID: b48362d8aaf32aeb4a75f5c556c652ffeeb1be5d
Gitweb: http://git.kernel.org/tip/b48362d8aaf32aeb4a75f5c556c652ffeeb1be5d
Author: Frederic Weisbecker <[email protected]>
AuthorDate: Tue, 18 Aug 2015 16:18:29 +0200
Committer: Thomas Gleixner <[email protected]>
CommitDate: Tue, 18 Aug 2015 18:36:59 +0200
hrtimer: Unconfuse switch_hrtimer_base() a bit
The variable called "this_base" is confusing because its name suggests
it's of "struct hrtimer_clock_base" type, along with "base" and "new_base"
which doesn't help understanding this complicated function.
Make its name clearer and fix the misleading comment while at it.
[ tglx: Fixed the comment for real ]
Signed-off-by: Frederic Weisbecker <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
---
kernel/time/hrtimer.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index f9eb21b..5c4fe50 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -196,18 +196,27 @@ struct hrtimer_cpu_base *get_target_base(struct hrtimer_cpu_base *base,
#endif
/*
- * Switch the timer base to the current CPU when possible.
+ * We switch the timer base to a power-optimized selected CPU target,
+ * if:
+ * - NO_HZ_COMMON is enabled
+ * - timer migration is enabled
+ * - the timer callback is not running
+ * - the timer is not the first expiring timer on the new target
+ *
+ * If one of the above requirements is not fulfilled we move the timer
+ * to the current CPU or leave it on the previously assigned CPU if
+ * the timer callback is currently running.
*/
static inline struct hrtimer_clock_base *
switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
int pinned)
{
- struct hrtimer_cpu_base *new_cpu_base, *this_base;
+ struct hrtimer_cpu_base *new_cpu_base, *this_cpu_base;
struct hrtimer_clock_base *new_base;
int basenum = base->index;
- this_base = this_cpu_ptr(&hrtimer_bases);
- new_cpu_base = get_target_base(this_base, pinned);
+ this_cpu_base = this_cpu_ptr(&hrtimer_bases);
+ new_cpu_base = get_target_base(this_cpu_base, pinned);
again:
new_base = &new_cpu_base->clock_base[basenum];
@@ -229,19 +238,19 @@ again:
raw_spin_unlock(&base->cpu_base->lock);
raw_spin_lock(&new_base->cpu_base->lock);
- if (new_cpu_base != this_base &&
+ if (new_cpu_base != this_cpu_base &&
hrtimer_check_target(timer, new_base)) {
raw_spin_unlock(&new_base->cpu_base->lock);
raw_spin_lock(&base->cpu_base->lock);
- new_cpu_base = this_base;
+ new_cpu_base = this_cpu_base;
timer->base = base;
goto again;
}
timer->base = new_base;
} else {
- if (new_cpu_base != this_base &&
+ if (new_cpu_base != this_cpu_base &&
hrtimer_check_target(timer, new_base)) {
- new_cpu_base = this_base;
+ new_cpu_base = this_cpu_base;
goto again;
}
}