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| author | Chris Wilson <chris@chris-wilson.co.uk> | 2020-02-28 16:17:13 +0300 |
|---|---|---|
| committer | Chris Wilson <chris@chris-wilson.co.uk> | 2020-02-29 01:03:41 +0300 |
| commit | 062444bbc6859dbe9991673ffd377a4af4d76d51 (patch) | |
| tree | 6dfa9be3ece237031f47c7ffc5ae2ffdf70533cd /drivers/gpu/drm/i915/Kconfig.profile | |
| parent | 1a2695a7465971f28d8c44d6a282b6a2dd91e96f (diff) | |
| download | linux-062444bbc6859dbe9991673ffd377a4af4d76d51.tar.xz | |
drm/i915/gt: Expose busywait duration to sysfs
We busywait on an inflight request (one that is currently executing on
HW, and so might complete quickly) prior to setting up an interrupt and
sleeping. The trade off is that we keep an expensive CPU core busy in
order to avoid wake up latency: where that trade off should lie is best
left to the sysadmin.
The busywait mechanism can be compiled out with
./scripts/config --set-val DRM_I915_SPIN_REQUEST 0
The maximum busywait duration can be adjusted per-engine using,
/sys/class/drm/card?/engine/*/ms_busywait_duration_ns
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Steve Carbonari <steven.carbonari@intel.com>
Tested-by: Steve Carbonari <steven.carbonari@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200228131716.3243616-4-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/gpu/drm/i915/Kconfig.profile')
| -rw-r--r-- | drivers/gpu/drm/i915/Kconfig.profile | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile index d8d4a16179bd..9ee3b59685b9 100644 --- a/drivers/gpu/drm/i915/Kconfig.profile +++ b/drivers/gpu/drm/i915/Kconfig.profile @@ -35,9 +35,9 @@ config DRM_I915_PREEMPT_TIMEOUT May be 0 to disable the timeout. -config DRM_I915_SPIN_REQUEST - int "Busywait for request completion (us)" - default 5 # microseconds +config DRM_I915_MAX_REQUEST_BUSYWAIT + int "Busywait for request completion limit (ns)" + default 8000 # nanoseconds help Before sleeping waiting for a request (GPU operation) to complete, we may spend some time polling for its completion. As the IRQ may @@ -45,6 +45,9 @@ config DRM_I915_SPIN_REQUEST check if the request will complete in the time it would have taken us to enable the interrupt. + This is adjustable via + /sys/class/drm/card?/engine/*/max_busywait_duration_ns + May be 0 to disable the initial spin. In practice, we estimate the cost of enabling the interrupt (if currently disabled) to be a few microseconds. |