CFQ vs Deadline on phablet. Some analysis.

[Tim Gardner]

On 07/11/2013 03:17 AM, Colin Ian King wrote:
> Hi,
> 
> A while ago we I did some analysis on different I/O schedulers for
> Ubuntu and we concluded that deadline was in general a better choice of
> scheduler.  For the mobile devices, the Android default is CFQ which is
> curious, so I did some analysis to see if there was any compelling
> reason why this was so.
> 
> I've exercised the Nexus 4 with various file system tests (tiobench,
> bonnie++) and measured current drawn. The evidence shows that deadline
> draws marginally less current than CFQ and because it completes a little
> faster over all it consumes less power - ~3.5-5.5% less on tiobench and
> ~3.2% for bonnie++.
> 
> I've boot tested CFQ vs Deadline 10 times on maguro, mako, manta and
> grouper and the boot time to the point where /etc/rc.local is executed
> is faster too:
> 
> maguro: 6.5%
> mako: 0.9%
> manta: 0.1%
> grouper: 12.3%
> 
> so a varied improvement depending on number of CPUs, CPU speed, etc. But
> no obvious regressions.
> 
> http://kernel.ubuntu.com/~cking/pm-arm/kernel-tweaks/mobile-cfq-vs-deadline-power.ods
> 
> Anyhow, I can't see any compelling reason why Android has CFQ by default
> and why we shouldn't move to Deadline.
> 
> Colin
> 

Applied to all Nexus kernels and uploaded.

-- 
Tim Gardner tim.gardner at canonical.com