Commit 868a3e91 authored by Thomas Gleixner's avatar Thomas Gleixner

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: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarPreeti U Murthy <preeti@linux.vnet.ibm.com>
Acked-by: default avatarPeter 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.deSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
parent 21d6d52a
...@@ -163,7 +163,7 @@ enum hrtimer_base_type { ...@@ -163,7 +163,7 @@ enum hrtimer_base_type {
* and timers * and timers
* @cpu: cpu number * @cpu: cpu number
* @active_bases: Bitfield to mark bases with active timers * @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 * @expires_next: absolute time of the next event which was scheduled
* via clock_set_next_event() * via clock_set_next_event()
* @in_hrtirq: hrtimer_interrupt() is currently executing * @in_hrtirq: hrtimer_interrupt() is currently executing
...@@ -179,7 +179,7 @@ struct hrtimer_cpu_base { ...@@ -179,7 +179,7 @@ struct hrtimer_cpu_base {
raw_spinlock_t lock; raw_spinlock_t lock;
unsigned int cpu; unsigned int cpu;
unsigned int active_bases; unsigned int active_bases;
unsigned int clock_was_set; unsigned int clock_was_set_seq;
#ifdef CONFIG_HIGH_RES_TIMERS #ifdef CONFIG_HIGH_RES_TIMERS
ktime_t expires_next; ktime_t expires_next;
int in_hrtirq; int in_hrtirq;
......
...@@ -49,6 +49,7 @@ struct tk_read_base { ...@@ -49,6 +49,7 @@ struct tk_read_base {
* @offs_boot: Offset clock monotonic -> clock boottime * @offs_boot: Offset clock monotonic -> clock boottime
* @offs_tai: Offset clock monotonic -> clock tai * @offs_tai: Offset clock monotonic -> clock tai
* @tai_offset: The current UTC to TAI offset in seconds * @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 * @raw_time: Monotonic raw base time in timespec64 format
* @cycle_interval: Number of clock cycles in one NTP interval * @cycle_interval: Number of clock cycles in one NTP interval
* @xtime_interval: Number of clock shifted nano seconds in one NTP * @xtime_interval: Number of clock shifted nano seconds in one NTP
...@@ -85,6 +86,7 @@ struct timekeeper { ...@@ -85,6 +86,7 @@ struct timekeeper {
ktime_t offs_boot; ktime_t offs_boot;
ktime_t offs_tai; ktime_t offs_tai;
s32 tai_offset; s32 tai_offset;
unsigned int clock_was_set_seq;
struct timespec64 raw_time; struct timespec64 raw_time;
/* The following members are for timekeeping internal use */ /* The following members are for timekeeping internal use */
......
...@@ -451,7 +451,8 @@ static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base) ...@@ -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_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
ktime_t *offs_tai = &base->clock_base[HRTIMER_BASE_TAI].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 */ /* High resolution timer related functions */
......
...@@ -602,6 +602,9 @@ static void timekeeping_update(struct timekeeper *tk, unsigned int action) ...@@ -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_mono, &tk_fast_mono);
update_fast_timekeeper(&tk->tkr_raw, &tk_fast_raw); 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) ...@@ -1927,15 +1930,19 @@ void do_timer(unsigned long ticks)
/** /**
* ktime_get_update_offsets_now - hrtimer helper * 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_real: pointer to storage for monotonic -> realtime offset
* @offs_boot: pointer to storage for monotonic -> boottime offset * @offs_boot: pointer to storage for monotonic -> boottime offset
* @offs_tai: pointer to storage for monotonic -> clock tai 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() * 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 ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
ktime_t *offs_tai) ktime_t *offs_boot, ktime_t *offs_tai)
{ {
struct timekeeper *tk = &tk_core.timekeeper; struct timekeeper *tk = &tk_core.timekeeper;
unsigned int seq; unsigned int seq;
...@@ -1947,10 +1954,12 @@ ktime_t ktime_get_update_offsets_now(ktime_t *offs_real, ktime_t *offs_boot, ...@@ -1947,10 +1954,12 @@ ktime_t ktime_get_update_offsets_now(ktime_t *offs_real, ktime_t *offs_boot,
base = tk->tkr_mono.base; base = tk->tkr_mono.base;
nsecs = timekeeping_get_ns(&tk->tkr_mono); nsecs = timekeeping_get_ns(&tk->tkr_mono);
if (*cwsseq != tk->clock_was_set_seq) {
*cwsseq = tk->clock_was_set_seq;
*offs_real = tk->offs_real; *offs_real = tk->offs_real;
*offs_boot = tk->offs_boot; *offs_boot = tk->offs_boot;
*offs_tai = tk->offs_tai; *offs_tai = tk->offs_tai;
}
} while (read_seqcount_retry(&tk_core.seq, seq)); } while (read_seqcount_retry(&tk_core.seq, seq));
return ktime_add_ns(base, nsecs); return ktime_add_ns(base, nsecs);
......
...@@ -3,7 +3,8 @@ ...@@ -3,7 +3,8 @@
/* /*
* Internal interfaces for kernel/time/ * Internal interfaces for kernel/time/
*/ */
extern ktime_t ktime_get_update_offsets_now(ktime_t *offs_real, extern ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq,
ktime_t *offs_real,
ktime_t *offs_boot, ktime_t *offs_boot,
ktime_t *offs_tai); ktime_t *offs_tai);
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment