Abstract: For implementing the trade-off optimization between the execution time and cost of scientific workflow scheduling in cloud environment,this paper proposed a Time-Cost trade-off workflow Task Scheduling algorithm (TCTS) under bi-constrainted condition of deadline and budget.TCTS divides the solving process of the optimal schedu-ling scheme into two stages:the resource levelscheduling stage and the task level scheduling stage.In the resource level scheduling stage,the algorithm defines the priority of a task by the upward rank,and selects the suitable resource set satisfying bi-QoS constraints for tasks according to tasks’ rank.Further,in the task level scheduling stage,the algorithm defines four rules of selecting the optimal resource based upon Time-Cost trade-off,which can obtain the optimal workflow scheduling scheme.This paper elaborated the idea of the proposed algorithm by a designed example.Through the simulation tests of real-world scientific workflows,the proposed algorithm is compared with the same types of algorithms.The results show that under the constraint conditions with different tight degrees,the proposed algorithm has better perfor-mance on some indexes such as the scheduling cost,the scheduling time and the schedule success,which will effectively realize the balanced scheduling.

Key words: Budget constraint, Cloud computing environment, Multi-QoS constraint, Task’s priority, Workflow scheduling