Re: [PATCH 1/3] Separate IRQ-stacks from 4K-stacks option

[Ingo Molnar]

* Lee Revell <rlrevell@xxxxxxxxxxx> wrote:

> Yes, on a server you would probably disable threading for the disk and
> network IRQs (the VP patch lets you set this via /proc).  This feature
> effectively gives you IPLs on Linux, albeit only two of them. [...]

nono, this has no relation to IPLs. IPLs are a pretty crude hack to
implement exclusion on a very (and too) broad level. IRQ threading is a
way to serialize hardirq contexts into a process context and to make
them schedulable and preemptable. It basically 'flattens out' all the
hardirq nesting (and parallelism) that may happen on a default kernel
and together with softirq 'flattening' it creates a deterministic
execution environment.

it is not intended for servers, due to the overhead of redirection. It's
for realtime workloads and for latency-sensitive audio desktop
workloads. For servers and normal desktops the current IRQ and softirq
model is pretty OK.

	Ingo
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