[PATCH] drm/radeon: Inline r100_mm_rreg

[Lauri Kasanen]

On Fri, 11 Apr 2014 14:32:20 +0200
Christian König <deathsimple at vodafone.de> wrote:

> Am 11.04.2014 11:54, schrieb Lauri Kasanen:
> > On Fri, 11 Apr 2014 10:33:08 +0200
> > Christian König <deathsimple at vodafone.de> wrote:
> >
> >>>> Actually direct register access shouldn't be necessary so often. Apart
> >>>> from page flips, write/read pointer updates and irq processing there
> >>>> shouldn't be so many of them. Could you clarify a bit more what issue
> >>>> you are seeing here?
> >>> Too much cpu usage for such a simple function. 2% makes it #2 in top-10
> >>> radeon.ko functions, right after evergreen_cs_parse. For reference, #3
> >>> (radeon_cs_packet_parse) is only 0.5%, one fourth of this function's
> >>> usage.
> >> I think you misunderstood me here. I do believe your numbers that it
> >> makes a noticeable difference.
> >>
> >> But I've did a couple of perf tests recently on SI and CIK while hacking
> >> on VM support, and IIRC r100_mm_rreg didn't showed up in the top 10 on
> >> those systems.
> >>
> >> So what puzzles me is who the hack is calling r100_mm_rreg so often that
> >> it makes a noticeable difference on evergreen/NI?
> > The biggest caller is cayman_cp_int_cntl_setup. Before inlining it took
> > 0.0013%, after it takes 1%.
> 
> Sounds like somebody is constantly turning interrupts on and off.

I instrumented radeon_irq_set. There's about 12 calls to that per sec,
most coming from radeon_irq_kms_sw_irq_get and
radeon_irq_kms_sw_irq_put.

So from your earlier mail I gather this amount of IRQ setting is
normal. It's just taking a lot of cpu for some reason.

- Lauri