Scheduling computations with provably low synchronization overheads

We present a Work Stealing scheduling algorithm that provably avoids most synchronization overheads by keeping processors’ deques entirely private by default and only exposing work when requested by thieves. This is the first paper that obtains bounds on the synchronization overheads that are (essentially) independent of the total amount of work, thus corresponding to a great improvement, in both algorithm design and theory, over state-of-the-art Work Stealing algorithms. Consider any computation with work $$T_{1}$$ T 1 and critical-path length $$T_{\infty }$$ T ∞ executed by P processors using our scheduler. Our analysis shows that the expected execution time is $$O\left( \frac{T_{1}}{P} + T_{\infty }\right) $$ O T 1 P + T ∞ , and the expected synchronization overheads incurred during the execution are at most $$O\left( \left( C_{\mathrm{CAS}} + C_{\mathrm{MFence}}\right) PT_{\infty }\right) $$ O C CAS + C MFence P T ∞ , where $$C_{\mathrm{CAS}}$$ C CAS and $$C_{\mathrm{MFence}}$$ C MFence , respectively, denote the maximum cost of executing a Compare-And-Swap instruction and a Memory Fence instruction.