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If the preempted context takes too long to relinquish control, e.g. it is stuck inside a shader with arbitration disabled, evict that context with an engine reset. This ensures that preemptions are reasonably responsive, providing a tighter QoS for the more important context at the cost of flagging unresponsive contexts more frequently (i.e. instead of using an ~10s hangcheck, we now evict at ~100ms). The challenge of lies in picking a timeout that can be reasonably serviced by HW for typical workloads, balancing the existing clients against the needs for responsiveness. Note that coupled with timeslicing, this will lead to rapid GPU "hang" detection with multiple active contexts vying for GPU time. The forced preemption mechanism can be compiled out with ./scripts/config --set-val DRM_I915_PREEMPT_TIMEOUT 0 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191023133108.21401-2-chris@chris-wilson.co.uk
51 lines
2.1 KiB
Plaintext
51 lines
2.1 KiB
Plaintext
config DRM_I915_USERFAULT_AUTOSUSPEND
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int "Runtime autosuspend delay for userspace GGTT mmaps (ms)"
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default 250 # milliseconds
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help
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On runtime suspend, as we suspend the device, we have to revoke
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userspace GGTT mmaps and force userspace to take a pagefault on
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their next access. The revocation and subsequent recreation of
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the GGTT mmap can be very slow and so we impose a small hysteris
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that complements the runtime-pm autosuspend and provides a lower
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floor on the autosuspend delay.
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May be 0 to disable the extra delay and solely use the device level
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runtime pm autosuspend delay tunable.
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config DRM_I915_PREEMPT_TIMEOUT
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int "Preempt timeout (ms, jiffy granularity)"
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default 100 # milliseconds
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help
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How long to wait (in milliseconds) for a preemption event to occur
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when submitting a new context via execlists. If the current context
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does not hit an arbitration point and yield to HW before the timer
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expires, the HW will be reset to allow the more important context
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to execute.
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May be 0 to disable the timeout.
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config DRM_I915_SPIN_REQUEST
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int "Busywait for request completion (us)"
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default 5 # microseconds
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help
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Before sleeping waiting for a request (GPU operation) to complete,
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we may spend some time polling for its completion. As the IRQ may
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take a non-negligible time to setup, we do a short spin first to
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check if the request will complete in the time it would have taken
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us to enable the interrupt.
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May be 0 to disable the initial spin. In practice, we estimate
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the cost of enabling the interrupt (if currently disabled) to be
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a few microseconds.
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config DRM_I915_STOP_TIMEOUT
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int "How long to wait for an engine to quiesce gracefully before reset (ms)"
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default 100 # milliseconds
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help
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By stopping submission and sleeping for a short time before resetting
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the GPU, we allow the innocent contexts also on the system to quiesce.
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It is then less likely for a hanging context to cause collateral
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damage as the system is reset in order to recover. The corollary is
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that the reset itself may take longer and so be more disruptive to
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interactive or low latency workloads.
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