counter wars (jeeconf 2016)

АлексейФедоров,Одноклассники

CounterWars

Зачемвыздесь?

3 Много интересных докладов в других залах

4Counter

public interface Counter {

long get();

void increment();

}

5Simple Counter

class SimpleCounter implements Counter {

private long value = 0;

public long get() {return value;

}

public void increment() {value++;

}

}

6Volatile Counter

class VolatileCounter implements Counter {

volatile long value = 0;


}

public void increment() {value++;

}

}

7Volatile Counter

class VolatileCounter implements Counter {



}

public void increment() {long oldValue = value; // readlong newValue = oldValue + 1; // modifyvalue = newValue; // write

}}

8

class SynchronizedCounter implements Counter {


public synchronized long get() {return value;

}

public synchronized void increment() {value++;

}

}

Synchronized Counter

9Synchronized Counter

class SynchronizedCounter implements Counter {

long value = 0;

public synchronized long get() {return value;

}

public synchronized void increment() {value++;

}

}

10Тестовый стенд

Core(TM) i7-47704 x 2 x 2.0 Ghz (downscaled)

Linux Ubuntu 14.04.43.13.0-86-generic x86_64

taskset -c 0,1,2,3 (thread affinity)

11Бенчмарки, op/µs

Thanks to Nitsan Wakarthttp://psy-lob-saw.blogspot.ru/2014/06/jdk8-update-on-scalable-counters.html

1 thread 2 threads2 threads 2 threads4 threads8 threads

Core 0 Core 0 Cores 0,4 Cores 0,1Cores 0-3Cores 0-7

LONG 308 267 182 220 180 86

VOLATILE_LONG 77 77 79 22 21 35

SYNCHRONIZED 26 43 27 12 12 13

Вывод1:синхронизациячего-тостоит

13

class LockCounter implements Counter {

long value;final Lock lock = new ReentrantLock();

public long get() {try {

lock.lock();return value;

} finally {lock.unlock();

}

}

}

public void add() {try {

lock.lock();value += 1;


}}

Lock Counter

14Lock Counter






}

}

}




}}





REENTRANTLOCK 32 32 18 5 20 20

http://mechanical-sympathy.blogspot.com/2011/11/java-lock-implementations.htmlhttp://mechanical-sympathy.blogspot.com/2011/11/biased-locking-osr-and-benchmarking-fun.htmlhttp://www.javaspecialist.ru/2011/11/synchronized-vs-reentrantlock.htmlhttp://dev.cheremin.info/2011/11/synchronized-vs-reentrantlock.html

16






}

}

}




}}

Lock Counter

17


long value;final Lock lock = new ReentrantLock(true);




}

}

}




}}

Lock Counter





UNFAIR_LOCK 32 32 18 5 20 20

FAIR_LOCK

Насколькомедленнее,чемunfairlock?





UNFAIR_LOCK 32 32 18 5 20 20

FAIR_LOCK 31 5 ± 9 0.5 ± 0.3 0.26 0.24 0.23

Насколькомедленнее,чемunfairlock?Надвапорядка!


Насколькомедленнее,чемunfairlock?Надвапорядка!Страшнолиэто?




UNFAIR_LOCK 32 32 18 5 20 20

FAIR_LOCK 31 5 ± 9 0.5 ± 0.3 0.26 0.24 0.23

21Как устроен типичный Core i7

CPU4

CPU0

CPU5

CPU1

CPU6

CPU2

CPU7

CPU3

L1cache

L2cache

L1cache L1cache L1cache


L3cache

Вывод2:честностьчего-тостоит

Атомики иCAS

24CompareandSwap— HardwareSupport

compare-and-swapCAS

load-link / store-conditionalLL/SC

cmpxchg

ldrex/strex lwarx/stwcx

25 CAS Counterpublic class CasLoopCounter implements Counter {

private AtomicLong value = new AtomicLong();

public long get() {return value.get();

}

public void increment() {for (;;) {

long oldValue = value.get();long newValue = oldValue + 1;if (value.compareAndSet(oldValue, newValue))

return;}

}

}





UNFAIR_LOCK 32 32 18 5 20 20

CAS_LOOP





UNFAIR_LOCK 32 32 18 5 20 20

CAS_LOOP 62 62 45 10 6 5

28Get-and-Add Counter

public class CasLoopCounter implements Counter {

private AtomicLong value = new AtomicLong();

public long get() {return value.get();

}

public void increment() {value.getAndAdd(1);

}

}

29 AtomicLong.getAndAdd()





UNFAIR_LOCK 32 32 18 5 20 20

CAS_LOOP 62 62 45 10 6 5

GET_AND_ADD 100 100 97 27 28 28

31True Sharing

CPU4

CPU0

CPU5

CPU1

CPU6

CPU2

CPU7

CPU3

L1cache

L2cache



L3cache

32

atomicLong.getAndAdd(5)

JDK7u95 JDK8u72

60

9 7 6

100

27 27 27

1 2 3 4

ops/μs

threads

33


JDK7u95 JDK8u72

60

9 7 6

100

27 27 27

1 2 3 4

ops/μs

threads

34


JDK7u95 JDK8u72

60

9 7 6

100

27 27 27

1 2 3 4

ops/μs

threads

35

loop:mov 0x10(%rbx),%raxmov %rax,%r11add $0x5,%r11lock cmpxchg %r11,0x10(%rbx)sete %r11bmovzbl %r11b,%r11dtest %r10d,%r10dje loop

JDK7u95-XX:+PrintAssembly


36

lock addq $0x5,0x10(%rbp))loop:mov 0x10(%rbx),%raxmov %rax,%r11add $0x5,%r11lock cmpxchg %r11,0x10(%rbx)sete %r11bmovzbl %r11b,%r11dtest %r10d,%r10dje loop

JDK7u95-XX:+PrintAssembly JDK8u72 -XX:+PrintAssembly


JDK7u95 JDK8u72

60

9 7 6

100

27 27 27

1 2 3 4

ops/μs

threads

37 AtomicLong.getAndAdd()— JDK7


cmpxchg


lock addqJVMIntrinsic

Вывод3: неверьтевсему,чтонаписановисходникахOpenJDK

43StampedLock Counter

public class StampedLockCounter implements Counter {private long value = 0; private StampedLock lock = new StampedLock();

public long get() { ... }

public void add() {long stamp = lock.writeLock();try {

value++;} finally{

lock.unlock(stamp);}

}}





UNFAIR_LOCK 32 32 18 5 20 20

CAS_LOOP 62 62 45 10 6 5

GET_AND_ADD 100 100 97 27 28 28

STAMPED_LOCK 31 31 24 5 22 21

45Long Adder Counter

public class LongAdderCounter implements Counter {

private LongAdder value = new LongAdder();

public long get() {return value.longValue();

}

public void increment() {value.add(1);

}

}





UNFAIR_LOCK 32 32 18 5 20 20

CAS_LOOP 62 62 45 10 6 5

GET_AND_ADD 100 100 97 27 28 28

STAMPED_LOCK 31 31 24 5 22 21

LONG_ADDER 62 62 85 124 248 340

47Литература

48Материалы

• Все-все-все— bit.ly/concurrency-interest• Nitsan Wakart — psy-lob-saw.blogspot.com• АлексейШипилёв — shipilev.net

Вопросыиответы

counter wars (jeeconf 2016)

Engineering