Karmic I/O scheduler issues

Tim Gardner tim.gardner at canonical.com
Tue Sep 29 23:19:53 UTC 2009

John Mahoney wrote:
> On Tue, Sep 29, 2009 at 4:37 PM, Tim Gardner <tim.gardner at canonical.com>wrote:
>> 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.

Tim Gardner tim.gardner at canonical.com

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