Polled mode applications such as the Storage Performance Development Kit (SPDK) NVMe over Fabrics target can demonstrate higher performance and efficiency compared to applications with a more traditional interrupt-driven threading model. But this performance and efficiency comes at a cost of increased CPU core utilization when the application is lightly loaded or idle. This talk will introduce a new SPDK scheduler framework which enables transferring work between CPU cores for purposes of shutting down or lowering frequency on cores when under-utilized. We will first describe the SPDK architecture for lightweight threads. Next, we will introduce the scheduler framework and how a scheduler module can collect metrics on the running lightweight threads to make scheduling decisions. Finally, we will share initial results comparing SPDK NVMe-oF target performance and CPU efficiency of a new scheduler module based on this framework with the default static scheduler.

Learning Objectives: 1) Understand how work is scheduled in an SPDK polled mode application such as the NVMe over Fabrics target; 2) Understand how SPDK scheduler modules under the new framework can decide if and when to move work between CPU cores; 3) Understand how performance + CPU efficiency compare between the default scheduler and scheduler implemented in the new framework.