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authorThomas Gleixner <tglx@linutronix.de>2015-04-15 00:08:37 +0300
committerThomas Gleixner <tglx@linutronix.de>2015-04-22 18:06:49 +0300
commit868a3e915f7f5eba8f8cb4f7da2276760807c51c (patch)
treedcec10d02c9613b5cad4f32d6d3ed7352825b1c8
parent21d6d52a1b7028e6a6840bd82e354aefa9a5e203 (diff)
downloadlinux-868a3e915f7f5eba8f8cb4f7da2276760807c51c.tar.xz
hrtimer: Make offset update smarter
On every tick/hrtimer interrupt we update the offset variables of the clock bases. That's silly because these offsets change very seldom. Add a sequence counter to the time keeping code which keeps track of the offset updates (clock_was_set()). Have a sequence cache in the hrtimer cpu bases to evaluate whether the offsets must be updated or not. This allows us later to avoid pointless cacheline pollution. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: John Stultz <john.stultz@linaro.org> Link: http://lkml.kernel.org/r/20150414203501.132820245@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: John Stultz <john.stultz@linaro.org>
-rw-r--r--include/linux/hrtimer.h4
-rw-r--r--include/linux/timekeeper_internal.h2
-rw-r--r--kernel/time/hrtimer.c3
-rw-r--r--kernel/time/timekeeping.c23
-rw-r--r--kernel/time/timekeeping.h7
5 files changed, 26 insertions, 13 deletions
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index e292830b58f0..5e04f8fc26f6 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -163,7 +163,7 @@ enum hrtimer_base_type {
* and timers
* @cpu: cpu number
* @active_bases: Bitfield to mark bases with active timers
- * @clock_was_set: Indicates that clock was set from irq context.
+ * @clock_was_set_seq: Sequence counter of clock was set events
* @expires_next: absolute time of the next event which was scheduled
* via clock_set_next_event()
* @in_hrtirq: hrtimer_interrupt() is currently executing
@@ -179,7 +179,7 @@ struct hrtimer_cpu_base {
raw_spinlock_t lock;
unsigned int cpu;
unsigned int active_bases;
- unsigned int clock_was_set;
+ unsigned int clock_was_set_seq;
#ifdef CONFIG_HIGH_RES_TIMERS
ktime_t expires_next;
int in_hrtirq;
diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h
index fb86963859c7..6f8276ae579c 100644
--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -49,6 +49,7 @@ struct tk_read_base {
* @offs_boot: Offset clock monotonic -> clock boottime
* @offs_tai: Offset clock monotonic -> clock tai
* @tai_offset: The current UTC to TAI offset in seconds
+ * @clock_was_set_seq: The sequence number of clock was set events
* @raw_time: Monotonic raw base time in timespec64 format
* @cycle_interval: Number of clock cycles in one NTP interval
* @xtime_interval: Number of clock shifted nano seconds in one NTP
@@ -85,6 +86,7 @@ struct timekeeper {
ktime_t offs_boot;
ktime_t offs_tai;
s32 tai_offset;
+ unsigned int clock_was_set_seq;
struct timespec64 raw_time;
/* The following members are for timekeeping internal use */
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 9e111dd83ca3..8ce9b3138017 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -451,7 +451,8 @@ static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
ktime_t *offs_tai = &base->clock_base[HRTIMER_BASE_TAI].offset;
- return ktime_get_update_offsets_now(offs_real, offs_boot, offs_tai);
+ return ktime_get_update_offsets_now(&base->clock_was_set_seq,
+ offs_real, offs_boot, offs_tai);
}
/* High resolution timer related functions */
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index dd1efa6a4ea4..3365e32dc208 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -602,6 +602,9 @@ static void timekeeping_update(struct timekeeper *tk, unsigned int action)
update_fast_timekeeper(&tk->tkr_mono, &tk_fast_mono);
update_fast_timekeeper(&tk->tkr_raw, &tk_fast_raw);
+
+ if (action & TK_CLOCK_WAS_SET)
+ tk->clock_was_set_seq++;
}
/**
@@ -1927,15 +1930,19 @@ void do_timer(unsigned long ticks)
/**
* ktime_get_update_offsets_now - hrtimer helper
+ * @cwsseq: pointer to check and store the clock was set sequence number
* @offs_real: pointer to storage for monotonic -> realtime offset
* @offs_boot: pointer to storage for monotonic -> boottime offset
* @offs_tai: pointer to storage for monotonic -> clock tai offset
*
- * Returns current monotonic time and updates the offsets
+ * Returns current monotonic time and updates the offsets if the
+ * sequence number in @cwsseq and timekeeper.clock_was_set_seq are
+ * different.
+ *
* Called from hrtimer_interrupt() or retrigger_next_event()
*/
-ktime_t ktime_get_update_offsets_now(ktime_t *offs_real, ktime_t *offs_boot,
- ktime_t *offs_tai)
+ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
+ ktime_t *offs_boot, ktime_t *offs_tai)
{
struct timekeeper *tk = &tk_core.timekeeper;
unsigned int seq;
@@ -1947,10 +1954,12 @@ ktime_t ktime_get_update_offsets_now(ktime_t *offs_real, ktime_t *offs_boot,
base = tk->tkr_mono.base;
nsecs = timekeeping_get_ns(&tk->tkr_mono);
-
- *offs_real = tk->offs_real;
- *offs_boot = tk->offs_boot;
- *offs_tai = tk->offs_tai;
+ if (*cwsseq != tk->clock_was_set_seq) {
+ *cwsseq = tk->clock_was_set_seq;
+ *offs_real = tk->offs_real;
+ *offs_boot = tk->offs_boot;
+ *offs_tai = tk->offs_tai;
+ }
} while (read_seqcount_retry(&tk_core.seq, seq));
return ktime_add_ns(base, nsecs);
diff --git a/kernel/time/timekeeping.h b/kernel/time/timekeeping.h
index 4d177fce37d5..704f595ce83f 100644
--- a/kernel/time/timekeeping.h
+++ b/kernel/time/timekeeping.h
@@ -3,9 +3,10 @@
/*
* Internal interfaces for kernel/time/
*/
-extern ktime_t ktime_get_update_offsets_now(ktime_t *offs_real,
- ktime_t *offs_boot,
- ktime_t *offs_tai);
+extern ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq,
+ ktime_t *offs_real,
+ ktime_t *offs_boot,
+ ktime_t *offs_tai);
extern int timekeeping_valid_for_hres(void);
extern u64 timekeeping_max_deferment(void);