util/system/spin_wait.cpp


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

#include "spin_wait.h" 
#include "yield.h" 
#include "compat.h" 
#include "thread.h" 
#include "spinlock.h" 
 
#include <util/digest/numeric.h> 
#include <util/generic/utility.h> 
 
template <class T> 
static inline T RandomizeSleepTime(T t) noexcept {
    static TAtomic counter = 0; 
    const T rndNum = IntHash((T)AtomicIncrement(counter)); 
 
    return (t * (T)4 + (rndNum % t) * (T)2) / (T)5; 
} 
 
//arbitrary values 
#define MIN_SLEEP_TIME 500 
#define MAX_SPIN_COUNT 0x7FF
 
TSpinWait::TSpinWait() noexcept 
    : T(MIN_SLEEP_TIME) 
    , C(0) 
{ 
} 
 
void TSpinWait::Sleep() noexcept { 
    ++C; 
 
    if (C == MAX_SPIN_COUNT) { 
        ThreadYield(); 
    } else if ((C & MAX_SPIN_COUNT) == 0) { 
        usleep(RandomizeSleepTime(T)); 
 
        T = Min<unsigned>((T * 3) / 2, 20000); 
    } else { 
        SpinLockPause(); 
    } 
}