Reducing the inter processor migrations of the DP-WRAP scheduling

In this work, we consider the scheduling problem of a set of periodic implicit-deadline and synchronous tasks, on a real-time multiprocessor composed of m identical processors. Our contribution consists in improving the temporal distribution of DP-WRAP algorithm by reducing the number of migrations. Indeed, DP-WRAP algorithm assigns tasks randomly and does not take into account the cost of migrations which can reach (m-1) migrations in the worst case. Note that recent experiments upon real platforms show that the cost of migrations has an influence on global system performance. Instead of randomly assigning tasks, we have proposed a task assignment algorithm that has reduced significantly the number of migrations of the DP-WRAP. The first step of the proposed algorithm, based on the classical bin-packing heuristics, allows minimizing the number of migrant tasks, the second step consists in assigning efficiently the migrant tasks. Experimental simulations show that the number of migrations, compared to DP-WRAP, is significantly reduced. This reduction can reach 60%.