• Chris Wilson's avatar
    drm/i915/execlists: Set queue priority from secondary port · 15c83c43
    Chris Wilson authored
    We can refine our current execlists->queue_priority if we inspect
    ELSP[1] rather than the head of the unsubmitted queue. Currently, we use
    the unsubmitted queue and say that if a subsequent request is more
    important than the current queue, we will rerun the submission tasklet
    to evaluate the need for preemption. However, we only want to preempt if
    we need to jump ahead of a currently executing request in ELSP. The
    second reason for running the submission tasklet is amalgamate requests
    into the active context on ELSP[0] to avoid a stall when ELSP[0] drains.
    (Though repeatedly amalgamating requests into the active context and
    triggering many lite-restore is off question gain, the goal really is to
    put a context into ELSP[1] to cover the interrupt.) So if instead of
    looking at the head of the queue, we look at the context in ELSP[1] we
    can answer both of the questions more accurately -- we don't need to
    rerun the submission tasklet unless our new request is important enough
    to feed into, at least, ELSP[1].
    
    v2: Add some comments from the discussion with Tvrtko.
    v3: More commentary to cross-reference queue_request()
    
    References: f6322edd ("drm/i915/preemption: Allow preemption between submission ports")
    Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Cc: Michał Winiarski <michal.winiarski@intel.com>
    Cc: Michel Thierry <michel.thierry@intel.com>
    Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
    Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
    Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20180411103929.27374-1-chris@chris-wilson.co.uk
    15c83c43
intel_lrc.c 80.1 KB