Chciałem zabrać was w podróż ... Podróż, w której poznacie jak zbudowane są podstawowe bloki synchronizacji (zwane lockami), ich historię oraz działanie (przy okazji zbudujemy sobie kilka z nich). Mechanizmy które w nich zastosujemy będą wam potrzebne do zrozumienia problemu wydajnego programowania wielo-procesorowego.

1. LOCKANATOMY
AND
SCALABLEMULTICOREPROGRAMMING
Bartosz Adamczewski
@badamczewski01

2. LETMESTARTBYCITING:
"CONCURRENCYISHARD"
-EVERYPROGRAMMEREVER

3. NOTCONVINCED?!

4. HOWDOES'THIS'RELATETO
MULTICORE?

5. UHHOHH
Lock?
Condition Variable
Monitor
MCS Lock
Current Research
Credits

6. THREADINGSYSTEM

7. LOCK?
Mutual Exclusion.
public void Acquire() { /* take the ownership of the lock */ }
public void Release() { /* give up ownership of the lock */ }

8. LOCK?
Mutual Exclusion.

9. PETERSONSLOCK
Two variable state lock.
_interested = new bool[2];
public void Enter(int id) {
int he = 1 ‐ id;
_interested[id] = true;
_victim = id;
while (_interested[he] && _victim == id)
{
continue;
}
}
public void Exit(int id) {
_interested[id] = false;
}

10. VOLATILE?

11. VOLATILE?

12. SPINLOCK
What the name implies.
public void Acquire()
{
while (Interlocked.CompareExchange(ref locker, 1, 0) != 0)
}
public void Release()
{
Interlocked.Exchange(ref locker, 0);
}

13. LOCK?
Fundamental construct for correct multi-core programs.

14. CONDITIONVARIABLE
Don't (busy) wait, get noti ed instead!
public void Wait(Lock l)
{ /* release the lock, add thread1 to wait queue, sleep, acquire */ }
public void Signal()
{ /* remove the waiting thread1 from wait queue */ }

15. CONDITIONVARIABLE
Don't (busy) wait, get noti ed instead!

16. CONDITIONVARIABLE
public void Wait(Lock l) {
while (Interlocked.CompareExchange(ref busy, 1, 0) != 0) { }
l.Release();
WaitingThread curr = new WaitingThread();
waitQueue.Enqueue(curr);
busy = 0;
curr.Sleep();
l.Acquire();
}
public void Signal() {
while (Interlocked.CompareExchange(ref busy, 1, 0) != 0) { }
if (waitQueue.Count != 0) {
WaitingThread curr = waitQueue.Dequeue();
Interlocked.Exchange(ref curr.Cond, 1);
}
busy = 0;
}

17. CONDITIONVARIABLE
Busy waiting sucks! Use CondVar

18. MONITOR
Interface for Lock + CondVar
public void Enter() { /* take the ownership of the lock */ }
public void Exit() { /* give up ownership of the lock */ }
public void Wait() { /* release the lock, add thread1 to wait queue, sleep, acquire */ }
public void Pulse() { /* remove the waiting thread1 from wait queue */ }

19. MCSLOCK
Uncontended Cache Lines
public void Acquire() { /* take the ownership of the lock */ }
public void Release() { /* give up ownership of the lock */ }

20. MCSLOCK

21. THECONTENTIONPROBLEM

22. MCSLOCK
Decrease cache line contention at all cost!

23. FUTURERESEARCH

24. FUTURERESEARCH
CLH Queue Locks + HCLH
Lock Free + Wait Free Code
The Scalable Commutativity Rule (this is hot!)

25. THANKYOU!
Bartosz Adamczewski
@badamczewski01