20-24 September 2021
US/Pacific timezone

Use of eBPF in cpu scheduler

20 Sep 2021, 07:50
40m
Networking and BPF Summit/Virtual-Room (LPC Virtual)

Networking and BPF Summit/Virtual-Room

LPC Virtual

150
Networking & BPF Summit (Closed) BPF & Networking Summit

Speakers

Hao Luo (Google) Barret Rhoden (Google)

Description

eBPF has been used extensively in performance profiling and monitoring. In this talk, I will describe a set of eBPF applications that help monitor and enhance cpu scheduling performances. These applications include:

  • Profiling scheduling latencies. I will talk about an application of eBPF to collect scheduling latency stats.

  • Profiling resource efficiency. For background, I will first introduce the scheduler feature core scheduling which is developed for mitigating L1TF cpu vulnerability. Then I will introduce the eBPF feature ksym which enables this application and describe how eBPF can help report the forced idle time, a type of cpu usage inefficiency caused by core scheduling.

  • The third application of eBPF is to assist userspace scheduling. ghOSt is a framework open sourced by Google to enable general-purpose delegation of scheduling policy to userspace processes in a Linux environment. ghOSt uses BPF acceleration for policy actions that need to happen closer to scheduling edges. We use this to maximize CPU utilization (pick_next_task), minimize jitter (task_tick elision) and control tail latency (select_task_rq on wakeup). We are also experimenting with BPF to implement a scaled-down variant of the scheduling policy while upgrading the main userspace ghOSt agent.

I agree to abide by the anti-harassment policy I agree

Primary authors

Hao Luo (Google) Barret Rhoden (Google)

Presentation Materials