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authorAnna-Maria Gleixner <anna-maria@linutronix.de>2017-12-21 11:41:40 +0100
committerIngo Molnar <mingo@kernel.org>2018-01-16 02:35:46 +0100
commit3f0b9e8eec7262648ab9c8321bf931624ee5c10a (patch)
tree0d5a376e2c7d1c27a6f1969d7816938ca6ed797b /include/linux/hrtimer.h
parentc272ca58c3ec5631f4ab507489d9477f74efe645 (diff)
downloadlinux-3f0b9e8eec7262648ab9c8321bf931624ee5c10a.tar.gz
hrtimer: Store running timer in hrtimer_clock_base
The pointer to the currently running timer is stored in hrtimer_cpu_base before the base lock is dropped and the callback is invoked. This results in two levels of indirections and the upcoming support for softirq based hrtimer requires splitting the "running" storage into soft and hard IRQ context expiry. Storing both in the cpu base would require conditionals in all code paths accessing that information. It's possible to have a per clock base sequence count and running pointer without changing the semantics of the related mechanisms because the timer base pointer cannot be changed while a timer is running the callback. Unfortunately this makes cpu_clock base larger than 32 bytes on 32-bit kernels. Instead of having huge gaps due to alignment, remove the alignment and let the compiler pack CPU base for 32-bit kernels. The resulting cache access patterns are fortunately not really different from the current behaviour. On 64-bit kernels the 64-byte alignment stays and the behaviour is unchanged. This was determined by analyzing the resulting layout and looking at the number of cache lines involved for the frequently used clocks. Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de> Cc: Christoph Hellwig <hch@lst.de> Cc: John Stultz <john.stultz@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: keescook@chromium.org Link: http://lkml.kernel.org/r/20171221104205.7269-12-anna-maria@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/hrtimer.h')
-rw-r--r--include/linux/hrtimer.h20
1 files changed, 9 insertions, 11 deletions
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 28f267cf2851..1bae7b9f071d 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -118,9 +118,9 @@ struct hrtimer_sleeper {
};
#ifdef CONFIG_64BIT
-# define HRTIMER_CLOCK_BASE_ALIGN 64
+# define __hrtimer_clock_base_align ____cacheline_aligned
#else
-# define HRTIMER_CLOCK_BASE_ALIGN 32
+# define __hrtimer_clock_base_align
#endif
/**
@@ -129,18 +129,22 @@ struct hrtimer_sleeper {
* @index: clock type index for per_cpu support when moving a
* timer to a base on another cpu.
* @clockid: clock id for per_cpu support
+ * @seq: seqcount around __run_hrtimer
+ * @running: pointer to the currently running hrtimer
* @active: red black tree root node for the active timers
* @get_time: function to retrieve the current time of the clock
* @offset: offset of this clock to the monotonic base
*/
struct hrtimer_clock_base {
struct hrtimer_cpu_base *cpu_base;
- int index;
+ unsigned int index;
clockid_t clockid;
+ seqcount_t seq;
+ struct hrtimer *running;
struct timerqueue_head active;
ktime_t (*get_time)(void);
ktime_t offset;
-} __attribute__((__aligned__(HRTIMER_CLOCK_BASE_ALIGN)));
+} __hrtimer_clock_base_align;
enum hrtimer_base_type {
HRTIMER_BASE_MONOTONIC,
@@ -154,8 +158,6 @@ enum hrtimer_base_type {
* struct hrtimer_cpu_base - the per cpu clock bases
* @lock: lock protecting the base and associated clock bases
* and timers
- * @seq: seqcount around __run_hrtimer
- * @running: pointer to the currently running hrtimer
* @cpu: cpu number
* @active_bases: Bitfield to mark bases with active timers
* @clock_was_set_seq: Sequence counter of clock was set events
@@ -177,8 +179,6 @@ enum hrtimer_base_type {
*/
struct hrtimer_cpu_base {
raw_spinlock_t lock;
- seqcount_t seq;
- struct hrtimer *running;
unsigned int cpu;
unsigned int active_bases;
unsigned int clock_was_set_seq;
@@ -198,8 +198,6 @@ struct hrtimer_cpu_base {
static inline void hrtimer_set_expires(struct hrtimer *timer, ktime_t time)
{
- BUILD_BUG_ON(sizeof(struct hrtimer_clock_base) > HRTIMER_CLOCK_BASE_ALIGN);
-
timer->node.expires = time;
timer->_softexpires = time;
}
@@ -424,7 +422,7 @@ static inline int hrtimer_is_queued(struct hrtimer *timer)
*/
static inline int hrtimer_callback_running(struct hrtimer *timer)
{
- return timer->base->cpu_base->running == timer;
+ return timer->base->running == timer;
}
/* Forward a hrtimer so it expires after now: */