The default for the grid engine system is to start scheduling runs in a fixed schedule interval. A good feature of fixed intervals is that they limit the CPU time consumption of the qmaster and the scheduler. A bad feature is that fixed intervals choke the scheduler, artificially resulting in a limited throughput. Many compute farms have machines specifically dedicated to qmaster and the scheduler, and such setups provide no reason to choke the scheduler. See schedule_interval in sched_conf(5).
You can configure immediate scheduling by using the flush_submit_sec and flush_finish_sec parameters of the scheduler configuration. See Changing the Scheduler Configuration With QMON, and the sched_conf(5) man page.
If immediate scheduling is activated, the throughput of a compute farm is limited only by the power of the machine that is hosting sge_qmaster and the scheduler.