Massive power regression going 3.4->3.5

[James Bottomley]

On Tue, 2012-07-31 at 10:54 +0100, Chris Wilson wrote:
> On Tue, 31 Jul 2012 10:37:35 +0100, James Bottomley <James.Bottomley at HansenPartnership.com> wrote:
> > On Tue, 2012-07-31 at 09:28 +0100, Chris Wilson wrote:
> > > On Tue, 31 Jul 2012 09:06:42 +0100, James Bottomley <James.Bottomley at HansenPartnership.com> wrote:
> > > > Actually, bad news: it looks like the problem is drm:
> > > > 
> > > > on 3.5 killing X causes idle power to go 14W -> 5.9W
> > > > on 3.4.6 killing X causes idle power to go 6.8W -> 5.7W
> > > 
> > > The files that will be the most interesting to compare at first are:
> > > 
> > > /sys/kernel/debug/dri/0/i915_drpc_info
> > > /sys/kernel/debug/dri/0/i915_cur_delayinfo
> > > /sys/kernel/debug/dri/0/i915_fbc_status
> > 
> > This is for the good kernel 3.4.6
> > 
> > jejb at dabdike> cat /sys/kernel/debug/dri/0/i915_drpc_info
> > RC information accurate: yes
> > Video Turbo Mode: yes
> > HW control enabled: yes
> > SW control enabled: no
> > RC1e Enabled: no
> > RC6 Enabled: yes
> > Deep RC6 Enabled: no
> > Deepest RC6 Enabled: no
> > Current RC state: RC6
> > Core Power Down: no
> > jejb at dabdike> cat /sys/kernel/debug/dri/0/i915_cur_delayinfo
> > GT_PERF_STATUS: 0x00000d29
> > RPSTAT1: 0x00040d00
> > Render p-state ratio: 13
> > Render p-state VID: 41
> > Render p-state limit: 255
> > CAGF: 650MHz
> > RP CUR UP EI: 20459us
> > RP CUR UP: 172us
> > RP PREV UP: 0us
> > RP CUR DOWN EI: 0us
> > RP CUR DOWN: 0us
> > RP PREV DOWN: 0us
> > Lowest (RPN) frequency: 650MHz
> > Nominal (RP1) frequency: 650MHz
> > Max non-overclocked (RP0) frequency: 1100MHz
> > jejb at dabdike> cat /sys/kernel/debug/dri/0/i915_fbc_status
> > FBC disabled: disabled per module param (default off)
> > 
> > And the bad kernel 3.5
> > 
> > jejb at dabdike> cat /sys/kernel/debug/dri/0/i915_drpc_info
> > RC information accurate: yes
> > Video Turbo Mode: yes
> > HW control enabled: yes
> > SW control enabled: no
> > RC1e Enabled: no
> > RC6 Enabled: yes
> > Deep RC6 Enabled: no
> > Deepest RC6 Enabled: no
> > Current RC state: RC6
> > Core Power Down: no
> > RC6 "Locked to RPn" residency since boot: 0
> > RC6 residency since boot: 97671911
> > RC6+ residency since boot: 0
> > RC6++ residency since boot: 0
> > jejb at dabdike> cat /sys/kernel/debug/dri/0/i915_cur_delayinfo
> > GT_PERF_STATUS: 0x00000d29
> > RPSTAT1: 0x00048d00
> > Render p-state ratio: 13
> > Render p-state VID: 41
> > Render p-state limit: 255
> > CAGF: 650MHz
> > RP CUR UP EI: 63719us
> > RP CUR UP: 26us
> > RP PREV UP: 0us
> > RP CUR DOWN EI: 0us
> > RP CUR DOWN: 0us
> > RP PREV DOWN: 0us
> > Lowest (RPN) frequency: 650MHz
> > Nominal (RP1) frequency: 650MHz
> > Max non-overclocked (RP0) frequency: 1100MHz
> > jejb at dabdike> cat /sys/kernel/debug/dri/0/i915_fbc_status
> > FBC disabled: disabled per module param (default off)
> 
> Ok, that rules out the the easy case of rc6 being disabled or not
> functioning at all, which could easily account for 6W.
> 
> When did you inspect the debug files? One effect I can imagine is that
> if your system was previously stuck at RPn and never upclocking the GPU
> when X starts. The question would then be what is preventing the GPU
> from reaching its lowest power state again.

After I logged into an xfce4 session and powertop showed idle had been
reached.

James