Re: [PATCH V3 00/11] block-throttle: add .high limit

[Linus Walleij]

On Tue, Oct 4, 2016 at 9:14 PM, Tejun Heo <tj@xxxxxxxxxx> wrote:

> I get that bfq can be a good compromise on most desktop workloads and
> behave reasonably well for some server workloads with the slice
> expiration mechanism but it really isn't an IO resource partitioning
> mechanism.

Not just desktops, also Android phones.

So why not have BFQ as a separate scheduling policy upstream,
alongside CFQ, deadline and noop?

I understand the CPU scheduler people's position that they want
one scheduler for everyone's everyday loads (except RT and
SCHED_DEADLINE) and I guess that is the source of the highlander
"there can be only one" argument, but note this:

kernel/Kconfig.preempt:

config PREEMPT_NONE
        bool "No Forced Preemption (Server)"
config PREEMPT_VOLUNTARY
        bool "Voluntary Kernel Preemption (Desktop)"
config PREEMPT
        bool "Preemptible Kernel (Low-Latency Desktop)"

We're already doing the per-usecase Kconfig thing for preemption.
But maybe somebody already hates that and want to get rid of it,
I don't know.

Yours,
Linus Walleij