Re: [PATCH 0/2] [tip: sched/core] sched: Disable PLACE_LAG and RUN_TO_PARITY and move them to sysctl

[Peter Zijlstra]

On Tue, Feb 11, 2025 at 11:41:13PM -0600, Cristian Prundeanu wrote:

> Your find also helps to point out that even when it works, SCHED_BATCH is 
> a more complex and error prone mitigation than just disabling PL and RTP. 
> The same reproducer setup that uses systemd to set SCHED_BATCH does show 
> improvement in 6.12, but not in 6.13+. There may not even be a single 
> approach that works well on both.
> 
> Conversely, setting NO_PLACE_LAG + NO_RUN_TO_PARITY is simply done at boot 
> time, and does not require further user effort. 

For your workload. It will wreck other workloads.

Yes, SCHED_BATCH might be more fiddly, but it allows for composition.
You can run multiple workloads together and they all behave.

Maybe the right thing here is to get mysql patched; so that it will
request BATCH itself for the threads that need it.