The last level cache (LLC) in private configurations offer lower latency and isolation but extinguishes the possibility of sharing underutilized cache resources. Cooperative Caching (CC) provides capacity sharing by spilling a line evicted from one cache to another. Current studies focus on efficient capacity sharing, while the adaptability of CC to manycore environment deserves more attentions. In this paper, we present Set-granular Regional Distributed Cooperative Caching to optimize CC in manycore CMPs with private LLCs. We achieve efficient capacity sharing by a low-traffic global receiver tracking mechanism and provide a method to manage set-grain cache state transitions for exclusive LLCs. Experiment results show that SRDCC performs better than baseline system, running different workloads varying in receiver-spiller number and distribution, in execution time up to 15.55 percent and memory access up to 40.25 percent, at a negligible cost of network traffics (6.21 percent more than baseline system at worst).