Fixing with Tejun's correct email address again. ;-) On 2/19/2024 4:11 AM, Joel Fernandes wrote: > > > On 2/19/2024 3:48 AM, Muhammad Usama Anjum wrote: >> On Fri, 2024-01-26 at 15:59 -0600, David Vernet wrote: >>> Hello, >>> >>> A few more use cases have emerged for sched_ext that are not yet >>> supported that I wanted to discuss in the BPF track. Specifically: >>> >>> - EAS: Energy Aware Scheduling >>> >>> While firmware ultimately controls the frequency of a core, the kernel >>> does provide frequency scaling knobs such as EPP. It could be useful for >>> BPF schedulers to have control over these knobs to e.g. hint that >>> certain cores should keep a lower frequency and operate as E cores. >>> This could have applications in battery-aware devices, or in other >>> contexts where applications have e.g. latency-sensitive >>> compute-intensive workloads. >> The current scheduler must already be using the frequency scaling >> knobs. Can sched_ext use those knobs directly with hint from userspace >> easily? > > With regards to the current way of doing things, it depends. On Intel platforms, > if HWP is enabled (Hardware-Controlled Performance States) which it is on almost > all Intel platforms I've seen, then the selection of the individual Performance > states (P-states) is done by the hardware, not the OS. My understanding is the > benefit of HWP is responsiveness of the state selection. So the only thing OS > can control then is either Turbo boost, or EPP. Unfortunately, this hinders > using an energy model and doing energy calculations (ex. If I place shit on this > core instead of that, then the total system power is such and such because > P-state on this core is this) the way EAS on ARM does. But maybe we can do > something simple with what is available and reap some benefits. > > On ARM platforms, there is more finer grained OS control of different operating > performance points (what they call OPP). > > Thanks.
