SRU IO Scheduler in Kubuntu 14.04

[Marc Deslauriers]

On 2014-10-14 11:08 AM, Martin Pitt wrote:
> Hello Harald, hello TB,
> 
> Harald Sitter [2014-10-08 17:03 +0200]:
>> I would like to kindly request the TBs input on a possible IO
>> scheduler changing SRU for Kubuntu 14.04.
> 
> I followed the discussion in the other thread (on u-devel@?).
> 
>> As seen in comment #5 of [2] it was suggested to wait until after the
>> release of 14.10 and only then proceed with the SRU. Most Kubuntu devs
>> do not appear to agree with this as being too conservative an
>> approach. The possible fallout is highly limited in impact (could only
>> make some things slower) and scope (only could do so on Kubuntu with
>> HDD).
> 
> I don't agree with the "highly limited in impact", but I do agree with
> the compromise of putting the udev rule into kubuntu-default-settings.
> While this isn't an appropriate long-term solution (i. e. it
> definitively shouldn't be done that way in Utopic or at least not in
> V), I don't know of a more appropriate place for an SRU.

The change to the Deadline scheduler also improves responsiveness when a desktop
user is copying large files or using VM software. I suspect switching this back
to CFQ will improve issues with Balloo, at the expense of Kubuntu users who copy
large files or use virtual machines. For this reason, I also disagree this
change is limited in impact.


> 
>> Would the technical board support a swifter resolution of the problem
>> or indeed prefer waiting?
> 
> I think we shouldn't wait with landing that change in -proposed, but
> do it now so that we can start collecting feedback and doing
> measurements on this. This will require quite extensive
> verification/testing on various hardware, which certainly won't be
> done by next week. This should include some positive results for
> KDE+balloo on HDD, confirm that the scheduler isn't changed for
> KDE+balloo on SSD, and that running Unity/zeitgeist with
> kubuntu-default-settings installed doesn't show a significant
> regression (some minor timing changes are acceptable, I think).

Marc.