[Bug 474977] [NEW] Stock ubuntu desktop kernel should be using 1000hz timer resolution
seivadmas at gmail.com
Thu Nov 5 01:43:38 UTC 2009
Public bug reported:
The standard ubuntu kernel uses 100hz timer resolution (for amd64, 250hz
for x86). I don't know why this is, I'm assuming it's just used because
it's the kernel default or something?
Either way it's not ideal for typical desktop usage, 100hz especially
really does introduce noticeable lag, can cause skips in audio and just
generally makes the whole desktop tend to microstutter a bit. According
to Con Kolivas (the guy who used to maintain the -ck patches and who
wrote the original completely fair scheduler for linux) the kernel devs
ran a lot of tests and for most desktop use cases the performance impact
was negligable, in some corner cases it caused up to a 1% performance
drop, whereas the desktop interactivity gains were very noticeable by
DISCLAIMER: Of course it's always hard to justify these sorts of claims
because desktop responsiveness is a notoriously woolly and hard to
measure thing, but without at least suggesting some solutions I don't
see how we can improve it, hence this bug report.
Personally I think that a 1% performance drop is totally acceptable on a
desktop in order to obtain a much smoother running system. In my opinion
(one which I'd sincerely hope most people here share) we should be
aiming at making Ubuntu Desktop the best desktop O/S you can have, which
means providing the best user experience. With lower resolution timers,
you can occasionally have audio skipping, your mouse inputs aren't
always responded to quite as fast, your compiz is a bit more jerky, your
games can sometimes lag for fractions of a second etc etc etc. Just
general responsiveness suffers in the case of low res timers.
Now I know these sort of claims are often made and because it's desktop
interactivity, it's very hard to prove anything because it's subjective,
but I encourage anybody reading this to compile a kernel with both 100hz
timers and 1000hz timers and have a play around, just use the desktop
like you normally would, typing text, moving windows, playing music etc.
I'm sure you will notice quite a difference. And hey, if I don't report
a bug and encourage some discussion on the topic, nothing gets done at
all, which is much worse ;-).
USER PID ACCESS COMMAND
/dev/snd/controlC1: sam 2051 F.... pulseaudio
/dev/snd/pcmC1D0c: sam 2051 F...m pulseaudio
/dev/snd/controlC0: sam 2051 F.... pulseaudio
/dev/snd/pcmC0D0p: sam 2051 F...m pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card hw:0 'Revolution71'/'M Audio Revolution-7.1 at 0xec00, irq 17'
Mixer name : 'ICE1724 - multitrack'
Components : ''
Controls : 27
Simple ctrls : 22
Card hw:1 'Intel'/'HDA Intel at 0xf9ff8000 irq 22'
Mixer name : 'Realtek ALC1200'
Components : 'HDA:10ec0888,104382fe,00100101'
Controls : 40
Simple ctrls : 22
Date: Thu Nov 5 01:20:24 2009
DistroRelease: Ubuntu 9.10
MachineType: System manufacturer P5QL PRO
Package: linux-generic 22.214.171.124.27
ProcCmdLine: root=UUID=f9c198f6-df39-49bf-9444-a1ad71d16bf6 ro elevator=deadline quiet splash
Uname: Linux 126.96.36.199-bfs304-test-ice1724patch x86_64
dmi.bios.vendor: American Megatrends Inc.
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: P5QL PRO
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: Rev 1.xx
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.product.name: P5QL PRO
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer
** Affects: linux-meta (Ubuntu)
** Tags: amd64 apport-bug
Stock ubuntu desktop kernel should be using 1000hz timer resolution
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