why did Ubuntu turn off kernel preemption in Edgy?
grasshopper at linuxkungfu.org
Sun Nov 26 22:05:11 GMT 2006
Thus spake Adam Dingle:
> In the Edgy kernel we've turned off CONFIG_PREEMPT, turning on
> CONFIG_PREEMPT_VOLUNTARY instead (see the changelog excerpt below). This
> change may not be great for multimedia users (especially those
> editing audio) since it can increase latency. Out of curiosity, what was
> the motivation for this?
I asked the same thing on #ubuntu-kernel on freenode. After first being told
that the kernel *was* preemptible, I eventually confirmed that we are only
preempting the Big Kernel Lock, which isn't the same thing, and it was
explained that it was decided that since kernel preemption may not be
appropriate for everyone, it was disabled. I suffer significantly from the
change, as my desktop gets mighty laggy during heavy i/o, of which there is
more than I would expect when I install packages.
As far as I can tell, CONFIG_PREEMPT is pretty well always appropriate on a
desktop machine. If not, I'm interested to know more, but I would very much
like a preemptible kernel.
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