IBM Working On More Linux CPU Power Usage Optimizations For Latency-Sensitive Workloads
Written by Michael Larabel in Linux Kernel on 7 May 2020 at 07:22 PM EDT. 8 Comments
LINUX KERNEL --
IBM engineers have been working on improvements to the Linux kernel's power savings while running latency-sensitive tasks but still delivering comparable performance. Their own numbers for a patched kernel are showing significant power saving benefits as much as ~20%.

The new patch series builds off earlier work published by IBM on providing a per-task "latency_nice" knob for scheduler hints. Latency_nice can be used for indicating latency requirements of a given task so the scheduler can make better decisions. With that latency_nice work published over recent months, among the use-cases talked about there was for better turbo/boost frequency decisions based upon grouping of tasks with similar latency requirements. Additionally, hypothetically having the scheduler not assign low-latency tasks to a CPU encountering AVX-512 based workloads where generally the core frequencies become quite limited.

With the new patches from IBM's Parth Shah is idle gating in the presence of latency-sensitive tasks. This work is about preventing the CPU idle governor from dropping to lower power levels when running a task indicated by latency_nice to be low-latency.

The proposed patches restrict the CPU running latency-sensitive tasks to go into any idle state in order to avoid the exit latency impact when needing to ramp back up to a higher power state.

The workloads benefiting the most from these patches are low-latency those that often go in a sleep-wake-sleep pattern like databases, GPU workloads, and other real-time applications. From IBM's own numbers, there was around a 20% improvement to the energy efficiency for a scheduler benchmark as well as around 20% for a PostgreSQL server.

We'll see where these idle gating patches lead as well as more broadly the latency_nice implementation and what other optimizations get possibly wired into benefiting from it.
Related News
About The Author
Author picture

Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

Popular News This Week