Load Balancing in Heterogeneous Processors
Omar Darwish
Load balancing is the process of improving the performance of a parallel and distributed system through a redistribution of load among the processors.
Definition
Who Initialized the load balancing algorithm ?
Sender Initiated◦ Initialized by the sender.◦ Sender sends request messages till it finds a
receiver that can accept the load.
Receiver Initiated◦ Initiated by the receiver.◦ Receiver sends request messages till it finds a
sender that can get the load.
Types of Load Balancing Algorithms
The performance of the processors is determined at the beginning of execution.
Master processor and slave processors.
A task is always executed on the processor to
which it is assigned. Reduce the execution time, minimizing the
communication delays
Static Load Balancing
Round Robin Algorithm◦ Processor choosing is performed in series and will
be back to the first processor if the last processor has been reached.
Randomized Algorithm◦ Uses random numbers to choose slave processors
based on statistics .
Static Algorithms
Central Manager Algorithm◦ The central processor is able to gather all slave
processors load information◦ The chosen slave processor is the processor
having the least load Threshold Algorithm
◦ The processes are assigned immediately upon creation to hosts.
◦ Under loaded, medium and overloaded.
Static Algorithms Cont…
Dynamic algorithms allocate processes dynamically when one of the processors becomes under loaded.
Buffered in the queue
Allocated dynamically upon requests from remote hosts
Dynamic Load Balancing
Central Queue◦ Stores new activities and unfulfilled requests as a
cyclic FIFO queue on the main host.
Local Queue
A parameter defines the minimal number of ready processes the load manager attempts to provide on each processor
Dynamic Load Balancing Algorithms
Adaptability ◦ Static No, Dynamic Yes
Predictability ◦ Static Yes, Dynamic No
Waiting Time (Queuing time )
Execution System
Performance Analysis of Load Balancing Algorithms
Fitness Function ◦ The main objective of GA is to find a schedule
with optimal cost while load-balancing. Less execution time. Less communication cost. Higher processor utilization. Maximum system throughput
Load Balancing in Distributed System using Genetic Algorithm
Selection Processors permutation
Crossover Exchange portions between strings.
Mutation Change the genes in a chromosome
(Processors set)
Cont…
NP complete problem.
Untractable with large N of tasks and P number of processors.
Optimal solution for Task allocation problem
Model description Actual execution cost
If we consider communication time, the work load L is
Cont…
Objective function
Weighted Round Robin
Processor 1 3 tasks/slot Processor 2 6 tasks/slot GCD =3
P1 P0 P1 P1 P0 P1 P1 P0 P1
Example :
O(n log log n/log n),
GCD in parallel
Static Algorithms
Round robin fashion
Heterogeneous processors
Weighting processors depends on capabilities
Fibonacci gives the high capabilities processors extra load.
Fibonacci & Linear Algorithms
Rank processors depends on capabilities
Give each processor weight depends on its rank (linearly or Fibonacci)
While (process<>0)◦ Assign tasks for each processor depends on its
weight
Psedocode
Linear approach Ex
◦ Ordering weights (1,2…,7)◦ 7 processors ◦ The highest capability takes weight 7◦ The lowest capability takes weight 1◦ Processor 7 will get 7 process each slot time◦ Processor 1will get 1 process each slot time
Example
Fibonacci approach Ex
◦ Ordering weights (1,1,2,3,5,8,13)◦ 7 processors ◦ The highest capability takes weight 13◦ The lowest capability takes weight 1
Processor 7 will get 13 process each slot time
Processor 1will get 1 process each slot time
Example
Framework
Load Balance
r
Tasks
P1
P2
P3
Distributing Tasks among different
processors
1 t 2 t 3 t 4 t 5 t 6 t 7 t
How can distribute N tasks (Linear)
Round1
1 t 2 t 3 t 4 t 5 t 6 t 7 tRound
2
Until No more tasks
1 t 1 t 2 t 3 t 5 t 8 t 13 t
How can distribute N tasks (Fibonacci )
Round1
1 t 1 t 2 t 3 t 5 t 8 t 13 tRound
2
Until No more tasks
M tasks K processors
How to distribute tasks among the processors
Less drops packets
Less time
System constraints
Number of processors N 6,7,8,9,10 Processors speed :
◦ High speeds (N/2) =0.10 * i i is the processor #◦ Low speeds (N/2) =0.03 * i i is the processor #
For example processor with id 6 can process 6.0*0.10*number of tasks in the Queue
Processor with id 2 can process 2.0*0.3*number of tasks in the Queue .
Memory For High speed computers 20 * i locationsFor low speed computers 320*i locations
1000 tasks Arrival packets =20, 33,….
Simulation Parameters
Results
5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.50
10
20
30
40
50
60
70
80
90
Dropped Packets
LinearFibonachi
# of processors
Dro
pped
Cont…
5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.50
10
20
30
40
50
60
Execution Time
Linear TimeFebonachi time
# of processors
Tim
e
Fibonacci distribution guarantee the more utilization of higher capabilities processors and less load on the less capabilities processors.
Cont…
The presentation explore:
◦ Static vs. Dynamic load balancing technique.
◦ The formulization of task scheduling problem.
Conclusion
Sharma, Sandeep, Sarabjit Singh, and Meenakshi Sharma. "Performance analysis of load balancing algorithms." World Academy of Science, Engineering and Technology 38 (2008): 269-272.
Rajguru, Abhijit A., and S. S. Apte. "A Comparative Performance Analysis of Load Balancing Algorithms in Distributed System using Qualitative Parameters." International Journal of Recent Technology and Engineering 1.3 (2012).
Shah, Purnima, and S. M. Shah. "Load Balancing in Distributed System Using Genetic Algorithm}." Special issues on IP Multimedia Communications}: 139-142.
Attiya, Gamal, and Yskandar Hamam. "Task allocation for minimizing programs completion time in multicomputer systems." Computational Science and Its Applications–ICCSA 2004. Springer Berlin Heidelberg, 2004. 97-106.
Chor, Benny, and Oded Goldreich. "An improved parallel algorithm for integer GCD." Algorithmica 5.1-4 (1990): 1-10.
http://kb.linuxvirtualserver.org/wiki/Weighted_Round-Robin_Scheduling
References
Questions ?