- Amin Vahdat
- Behnam Montazeri
- David E Culler
- Gautam Kumar
- Khaled Elmeleegy
- Luigi Rizzo
- Marc Asher de Kruijf
- Masoud Moshref
- Rachit Agarwal
- Saksham Agarwal
- Sylvia Ratnasamy
Abstract
We present evidence and characterization of host congestion in production clusters: adoption of high-bandwidth access links leading to emergence of bottlenecks within the host interconnect (NIC-to-CPU data path). We demonstrate that contention on existing IO memory management units and/or the memory subsystem can significantly reduce the available NIC-to-CPU bandwidth, resulting in hundreds of microseconds of queueing delays and eventual packet drops at hosts (even when running a state-of-the-art congestion control protocol that accounts for CPU-induced host congestion). We also discuss implications of host interconnect congestion to design of future host architecture, network stacks and network protocols.
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