performance Comparion of synchroniztion Operations + Intel Transactional Memory Operation

여러가지 멀티스레드 동기화 기법 중 어느 기법이 가장 성능이 좋을지 확인해봐라.

– 교수님 –

System Specification

CPU

rocky@dum:~$ lscpu
Architecture:          	x86_64
CPU op-mode(s):        	32-bit, 64-bit
Byte Order:            	Little Endian
CPU(s):                	32
On-line CPU(s) list:   	0-31
Thread(s) per core:   	2
Core(s) per socket:    	8
Socket(s):             	2
NUMA node(s):          	2
Vendor ID:             	GenuineIntel
CPU family:            	6
Model:                 	79
Model name:            	Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz
Stepping:              	1
CPU MHz:               	1200.843
CPU max MHz:           	3000.0000
CPU min MHz:           	1200.0000
BogoMIPS:              	4201.30
Virtualization:        	VT-x
L1d cache:             	32K
L1i cache:             	32K
L2 cache:              	256K
L3 cache:              	20480K
NUMA node0 CPU(s):    	0-7,16-23
NUMA node1 CPU(s):     	8-15,24-31

Memory

rocky@dum:~$ sudo dmidecode -t 17
# dmidecode 3.0
Getting SMBIOS data from sysfs.
SMBIOS 3.0.0 present.
Memory Device
Array Handle: 0x002A
Error Information Handle: Not Provided
Total Width: 72 bits
Data Width: 64 bits
Size: 8192 MB
Form Factor: DIMM
Set: None
Locator: P1-DIMMA1
Bank Locator: P0_Node0_Channel0_Dimm0
ype: DDR4
Type Detail: Synchronous
Speed: 2400 MHz
Manufacturer: Samsung
Serial Number: 2087B773
Asset Tag: P1-DIMMA1_AssetTag (date:17/38)
Part Number: M393A1G40EB1-CRC
Rank: 1
Configured Clock Speed: 2133 MHz
Minimum Voltage: Unknown
Maximum Voltage: Unknown
Configured Voltage: Unknown
  • Summary: Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz. 64아키텍처의 16물리 코어(하이퍼 스레딩, 32 논리 코어) 머신. NUMA 아키텍처로 2개의 socket(NUMA node)이 있으며, 각 socket당 8개 물리 코어가 있음. 메인 메모리는 DDR4의 8192MB 메모리가 4개 뱅크에 각각 위치하고 있으며 총 메인 메모리 공간은 32GB이다.

Intel(R) Xeon(R) CPU E5-2620에서 제공하는 Synchronization operations

1. Fetch And Add계열

type __sync_fetch_and_add (type *ptr, type value, ...)
type __sync_fetch_and_sub (type *ptr, type value, ...)
type __sync_fetch_and_or (type *ptr, type value, ...)
type __sync_fetch_and_and (type *ptr, type value, ...)
type __sync_fetch_and_xor (type *ptr, type value, ...)
type __sync_fetch_and_nand (type *ptr, type value, ...)

Note: These builtins perform the operation suggested by the name, and returns the value that had previously been in memory.

{ tmp = *ptr; *ptr op= value; return tmp; }
{ tmp = *ptr; *ptr = ~tmp & value; return tmp; }   // nand

2. Add And Fetch계열

type __sync_add_and_fetch (type *ptr, type value, ...)
type __sync_sub_and_fetch (type *ptr, type value, ...)
type __sync_or_and_fetch (type *ptr, type value, ...)
type __sync_and_and_fetch (type *ptr, type value, ...)
type __sync_xor_and_fetch (type *ptr, type value, ...)
type __sync_nand_and_fetch (type *ptr, type value, ...)

Note: These builtins perform the operation suggested by the name, and return the new value.

{ *ptr op= value; return *ptr; }
{ *ptr = ~*ptr & value; return *ptr; }   // nand

3. Compare And Swap

type __sync_val_compare_and_swap (type *ptr, type oldval type newval, ...)

Note: These builtins perform an atomic compare and swap. That is, if the current value of *ptr is oldval, then write newval into *ptr.

4. Memory Barrier

__sync_synchronize (...)

Note: This builtin issues a full memory barrier.

5. Test And Set

type __sync_lock_test_and_set (type *ptr, type value, ...)

Note: This builtin, as described by Intel, is not a traditional test-and-set operation, but rather an atomic exchange operation. It writes value into *ptr, and returns the previous contents of *ptr.

void __sync_lock_release (type *ptr, ...)

Note: This builtin releases the lock acquired by __sync_lock_test_and_set. Normally this means writing the constant 0 to *ptr.

Experimental Evaluation

single thread run과 동기화 기법들인 mutex lock, Compare-and-Swap, Fetch-and-Add, Add-and-Fetch, Test and Set(TAS를 이용한 mutual exclusion), Memory Barrier 총 6 가지를 사용하여 shared variable의 increment 성능 평가를 진행한다. Single thread를 제외한 6가지 방법에서는 32개 thread를 사용하였다.

Method Results(sec)
Single thread 3.041056455s
Mutex lock 133.816444880s
Fetch-and-Add 26.720684224s
Add-and-Fetch 26.909436926s
Compare-And-Swap 101.935627317s
Test-and-Set 1467.726637515s
Memory Barrier 324.967494416s

실험 결과에 따르면 single thread로 increment를 진행하였을 때, 가장 성능이 좋음을 알 수 있다. Variable의 increment와 같은 간단한 task는 task 자체보다 thread간 동기화로 발생하는 오버헤드가 더 크기 때문에 이런 결과가 발생하였다. 특히, shared variable를 1씩 increment하는 task는 task의 대부분(100%)가 atomic하게 실행되어야 할 정도로 간단하고 짧은 작업이기 때문에 위 결과와 같이 큰 차이를 보였다.