[Bug 93797] [BXT-P/APL] Low performance on UI, even without graphic interface

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93797

--- Comment #13 from Imre Deak <imre.deak at intel.com> ---
(In reply to Imre Deak from comment #12)
> (In reply to Imre Deak from comment #11)
> > (In reply to Elio from comment #10)
> > > Sure, in the middle time in setting maxcpus in grub with 1 and it looks a
> > > lot better.
> > 
> > Ok, I can confirm this, I can see it on my system as well now. This started
> > to happen when I upgraded to the BIOS I suggested to you in comment#9, so
> > probably that won't solve your problem. Booting with maxcpus=1 gets rid of
> > the issue for me too. I will try now different BIOS versions to see which
> > one is the latest that works.
> > 
> > Meanwhile this isn't a graphics driver issue, I can see the problem even if
> > I don't start the graphical interface, just by trying to type something on
> > the text console. I notified already the core people (Mika Westerberg), he
> > promised to take a look at this.
> 
> One more thing I noticed that this is somehow related to GFX RC6 state. If
> we disable that via BIOS (Uncore/Render:C6 disable, GT PM: disable) or by
> booting with i915.enable_rc6=0 then we also don't have the problem. I assume
> entering RC6 would enable some deeper CPU/system level power state, which
> could cause this lag.

Two other BIOS setup options under 'CPU Configuration'/'CPU Power Management'
to get rid of the lag (either one alone gets rid of the lag while having the
above RC6 and GT PM options enabled):
1. Max Core C State: 'Fused value'->'Core C6'
2. Max Package C State: 'S0ix default' -> 'C0'/'PC2'

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