Android 5.1 Lollipop brings non-trivial performance and efficiency improvements to the Nexus 6
Apparently, apart from improvements made to the ART runtime and any other possible optimizations of code, the new firmware also forces the Nexus 6's quad-core Qualcomm Snapdragon 805 processor to run all four cores at all times:
"... the device is now running full quad-core mode all the time which helps tremendously because the Kernel task scheduler can distribute the workload through all these cores so you'll get the perception that the device is not hanging anymore."
This is where your performance gain comes from. As for the part about better efficiency, we're told that Google has disabled something called 'built-in thread migration routines' that helps your battery survive for longer. Put simply, the feature basically kicks in whenever one task has to be migrated to a different from its current CPU core. In those instances, the task scheduler would before tell the destination core to match or exceed the current frequency of the origin core, lowering perceived lag. Since these migrations can apparently occur as often as every 20 ms, disabling them equals savings.
A good time to be a Nexus 6 user, no?
source: Google+
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