Karmic I/O scheduler issues
jmahoney at waav.com
Wed Sep 30 00:17:30 UTC 2009
On Tue, Sep 29, 2009 at 7:19 PM, Tim Gardner <tim.gardner at canonical.com>wrote:
> John Mahoney wrote:
> > On Tue, Sep 29, 2009 at 4:37 PM, Tim Gardner <tim.gardner at canonical.com
> >> I've been messing with I/O scheduler settings in the last couple of
> >> uploads. We found that CFQ has some serious issues that contributed to
> >> delayed boot times, so I changed the default to Deadline in
> >> 2.6.31-10.35. Scott Remnant reported that changing to Deadline shaved 40
> >> seconds off his boot.
> >> Since then I found this info: http://bugs.launchpad.net/bugs/436342
> >> I've been running a kernel with this patch and CFQ enabled. Perhaps some
> >> other folks could compare and contrast Deadline v.s. CFQ using their
> >> workloads. I find that CFQ is working a bit better then Deadline. I can
> >> run a 'make -j8' kernel build and still watch video while also playing
> >> music and reading email (without _too_ much stalling). Deadline is
> >> noticeably less smooth when the load average approaches 8.
> >> Adventurous types can try this kernel from
> >> http://kernel.ubuntu.com/~rtg/2.6.31-11-NEW_FAIR_SLEEPERS<http://kernel.ubuntu.com/%7Ertg/2.6.31-11-NEW_FAIR_SLEEPERS>
> >> (when its done copying)
> > It would be nice if Ubuntu had debugfs enabled by default so users could
> > more easily adjust these settings.
> > Such as discussed here: http://lkml.org/lkml/2008/5/2/67
> > Thanks,
> > John
> The debug file system is not mounted automagically. There are docs in
> the kernel tree at Documentation/filesystems/debugfs.txt.
What do you know.
sudo mount -t debugfs none /sys/kernel/debug
john at john-desktop:/sys/kernel/debug$ cat sched_features
NEW_FAIR_SLEEPERS NORMALIZED_SLEEPER WAKEUP_PREEMPT START_DEBIT
AFFINE_WAKEUPS CACHE_HOT_BUDDY SYNC_WAKEUPS NO_HRTICK NO_DOUBLE_TICK
ASYM_GRAN LB_BIAS LB_WAKEUP_UPDATE ASYM_EFF_LOAD NO_WAKEUP_OVERLAP
And like magic. Sorry for my ignorance.
Thanks for the enlightenment,
> Tim Gardner tim.gardner at canonical.com
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