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20d1c86a57
Use a ring-buffer like multi-version object structure which allows
always having a coherent object; we use this to avoid having to
disable IRQs while reading sched_clock() and avoids a problem when
getting an NMI while changing the cyc2ns data.
MAINLINE PRE POST
sched_clock_stable: 1 1 1
(cold) sched_clock: 329841 331312 257223
(cold) local_clock: 301773 310296 309889
(warm) sched_clock: 38375 38247 25280
(warm) local_clock: 100371 102713 85268
(warm) rdtsc: 27340 27289 24247
sched_clock_stable: 0 0 0
(cold) sched_clock: 382634 372706 301224
(cold) local_clock: 396890 399275 399870
(warm) sched_clock: 38194 38124 25630
(warm) local_clock: 143452 148698 129629
(warm) rdtsc: 27345 27365 24307
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-s567in1e5ekq2nlyhn8f987r@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
39 lines
1.0 KiB
C
39 lines
1.0 KiB
C
#ifndef _ASM_X86_TIMER_H
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#define _ASM_X86_TIMER_H
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#include <linux/init.h>
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#include <linux/pm.h>
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#include <linux/percpu.h>
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#include <linux/interrupt.h>
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#include <linux/math64.h>
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#define TICK_SIZE (tick_nsec / 1000)
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unsigned long long native_sched_clock(void);
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extern int recalibrate_cpu_khz(void);
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extern int no_timer_check;
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/*
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* We use the full linear equation: f(x) = a + b*x, in order to allow
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* a continuous function in the face of dynamic freq changes.
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*
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* Continuity means that when our frequency changes our slope (b); we want to
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* ensure that: f(t) == f'(t), which gives: a + b*t == a' + b'*t.
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*
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* Without an offset (a) the above would not be possible.
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*
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* See the comment near cycles_2_ns() for details on how we compute (b).
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*/
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struct cyc2ns_data {
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u32 cyc2ns_mul;
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u32 cyc2ns_shift;
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u64 cyc2ns_offset;
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u32 __count;
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/* u32 hole */
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}; /* 24 bytes -- do not grow */
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extern struct cyc2ns_data *cyc2ns_read_begin(void);
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extern void cyc2ns_read_end(struct cyc2ns_data *);
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#endif /* _ASM_X86_TIMER_H */
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