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[Bug 1188647] Re: Please change intel_pstate default to disable
For the decision to re-enable the intel pstate driver by default or not,
the suggestion is to be cautious. The driver keeps changing in rather
fundamental ways, such that one can never be sure how it is going to
perform. I will attach two graphs to (hopefully) help make my point.
The first graph demonstrates a dramatic difference in CPU frequency
scaling response as a function of load between kernel 3.12 and 3.15RC2
at a fixed idle (sleep) / work frequency.
The second graph (to be posted in a moment) demonstrates a dramatic
difference in CPU scaling frequency as a function of idle (sleep) /work
frequency at a fixed load.
Don't get me wrong here, as I am a proponent of the intel_pstate driver,
but I am concerned about how its response to stimulus keeps changing.
** Attachment added: "CPU 7 frequency vs load. Turbo on. Kernels 3.15RC2 and 3.12"
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Please change intel_pstate default to disable
Status in “linux” package in Ubuntu:
3.9 introduced a new default governor on SandyBridge CPUs called
INTEL_PSTATE which, when built in and enabled (the default), removes
all other governors (like our usual default, ondemand). 3.10 extended
this to Ivybridge generation CPUs.
In theory, this isn't an awful thing, as the new Intel pstate governor
should be higher performance and give better power savings. In
In practice, it drives my CPUs to max frequency nearly constantly,
spins my fans like mad and, somehow, does all of this while also
eating enough CPU time in kernel threads to make my machine choppy,
unresponsive, and unable to do simple things like play videos when I
get off work.
Therefore, I propose that we, for now, toggle intel_pstate to disable
by default (I am using intel_pstate=disable on my command line right
now, with great success), so it's still built in, and people can play
with it, but it's off by default.
DistroRelease: Ubuntu 13.10
Package: linux-image-3.9.0-4-generic 3.9.0-4.9
ProcVersionSignature: Ubuntu 3.9.0-4.9-generic 3.9.4
Uname: Linux 3.9.0-4-generic x86_64
USER PID ACCESS COMMAND
/dev/snd/controlC0: adconrad 2574 F.... pulseaudio
[ 30.633035] init: plymouth-stop pre-start process (2079) terminated with status 1
[ 36.086916] br0: port 1(eth0) entered forwarding state
Date: Fri Jun 7 08:48:56 2013
InstallationDate: Installed on 2012-12-09 (179 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Alpha amd64 (20121209)
MachineType: LENOVO 4173LPB
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.9.0-4-generic root=UUID=2222aad5-ef31-4428-973f-71740fc7cb6a ro intel_pstate=disable quiet splash vt.handoff=7
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.version: 8CET55WW (1.35 )
dmi.board.asset.tag: Not Available
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.version: Not Available
dmi.product.version: ThinkPad T420s
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