• Chris Wilson's avatar
    drm/i915/execlists: Virtual engine bonding · ee113690
    Chris Wilson authored
    Some users require that when a master batch is executed on one particular
    engine, a companion batch is run simultaneously on a specific slave
    engine. For this purpose, we introduce virtual engine bonding, allowing
    maps of master:slaves to be constructed to constrain which physical
    engines a virtual engine may select given a fence on a master engine.
    
    For the moment, we continue to ignore the issue of preemption deferring
    the master request for later. Ideally, we would like to then also remove
    the slave and run something else rather than have it stall the pipeline.
    With load balancing, we should be able to move workload around it, but
    there is a similar stall on the master pipeline while it may wait for
    the slave to be executed. At the cost of more latency for the bonded
    request, it may be interesting to launch both on their engines in
    lockstep. (Bubbles abound.)
    
    Opens: Also what about bonding an engine as its own master? It doesn't
    break anything internally, so allow the silliness.
    
    v2: Emancipate the bonds
    v3: Couple in delayed scheduling for the selftests
    v4: Handle invalid mutually exclusive bonding
    v5: Mention what the uapi does
    v6: s/nbond/num_bonds/
    Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
    Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20190521211134.16117-9-chris@chris-wilson.co.uk
    ee113690
i915_drm.h 67.4 KB