The GPU scheduler is needed for proper GPU resets and optimally utilizing the available hardware resources. The 31 patches for implementing the GPU scheduler will likely be merged for the Linux 4.3 kernel. However, for now with these patches the GPU scheduler is not enabled by default. Before being enabled, Alex is pursuing better integration with kernel fences and to clean-up the scheduler involvement in the ISR.
Right now the GPU scheduler has comparable performance to the non-scheduler paths but if you want to implement this support on a patched kernel you just need to set the amdgpu.enable_scheduler=1 kernel command-line option.
While waiting for Linux 4.3 or the work to appear in DRM-Next, the code can for now be found via the kernel mailing list. If you missed my recent AMDGPU Linux 4.2 tests, see The New AMD GPU Open-Source Driver On Linux 4.2 Works, But Still A Lot Of Work Ahead.