Are we still willing to pay the cost of moving include/linux/irqdesc.h into kernel/irq/?

Are we still willing to pay the cost of moving include/linux/irqdesc.h into kernel/irq/?

[Jiang Liu]

Hi Thomas,
	When refining irq related data structures, I found once we had
a plan to move include/linux/irqdesc.h into kernel/irq/, and I have
basic ideas about how to achieve the goal as:
1) de-inline accessor functions in irqdesc.h and move the declaration
   into linux/irq.h.
2) remove reference to irq_desc->xxxx from drivers one by one (this
   step is simple)
3) remove reference to irq_desc->xxxx from arch (this step is hard)
4) move irqdesc.h into kernel/irq/

But are we still willing to pay the cost of converting inline access
helpers into normal functions?
One possible tradeoff is to remove reference of irq_desc->xxxx from
drivers/, which is straight forward and shouldn't cause serious
performance regressions:)

Thanks!
Gerry

Re: Are we still willing to pay the cost of moving include/linux/irqdesc.h into kernel/irq/?

[Thomas Gleixner]

Jiang,

On Mon, 18 May 2015, Jiang Liu wrote:

> Hi Thomas,
> 	When refining irq related data structures, I found once we had
> a plan to move include/linux/irqdesc.h into kernel/irq/, and I have

I had that plan for two reasons:

  1) Is was tired of chasing the abuse of irq_desc

  2) We wanted to move irq descriptor memory allocation when
     affinity changes to a different node.

> basic ideas about how to achieve the goal as:
> 1) de-inline accessor functions in irqdesc.h and move the declaration
>    into linux/irq.h.
> 2) remove reference to irq_desc->xxxx from drivers one by one (this
>    step is simple)

Not sure. drivers/irqchip pretty much needs it and we have other
demeltiplex handlers which need it as well.

> 3) remove reference to irq_desc->xxxx from arch (this step is hard)

Same issue as #2

> 4) move irqdesc.h into kernel/irq/
> 
> But are we still willing to pay the cost of converting inline access
> helpers into normal functions?

I dont think so.

Thanks,

	tglx