Re: [PATCH 2/2] bcachefs: set rebalance thread to SCHED_BATCH and nice 19

[Peter Zijlstra]

On Tue, Jan 14, 2025 at 01:47:28PM +0100, Florian Schmaus wrote:
> While the rebalance thread is isually not compute bound, it does cause
> a considerable amount of I/O. Since "reducing" the nice level from 0
> to 19, also implicitly reduces the threads best-effort I/O scheduling
> class level from 4 to 7, the reblance thread's I/O will be depriotized
> over normal I/O.
> 
> Furthermore, we set the rebalance thread's scheduling class to BATCH,
> which means that it will potentially receive a higher scheduling
> latency. Making room for threads that need a low
> schedulinglatency (e.g., interactive onces).

sorta.. what worries me most about these patches are the claims without
backing numbers.

Supposedly there is a problem, and this here fixes it, but it doesn't
really get quantified much here.