mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-24 09:06:34 +07:00
6d2cb5aa38
The engine provides a mirror of the CSB in the HWSP. If we use the cacheable reads from the HWSP, we can shave off a few mmio reads per context-switch interrupt (which are quite frequent!). Just removing a couple of mmio is not enough to actually reduce any latency, but a small reduction in overall cpu usage. Much appreciation for Ben dropping the bombshell that the CSB was in the HWSP and for Michel in digging out the details. v2: Don't be lazy, add the defines for the indices. v3: Include the HWSP in debugfs/i915_engine_info v4: Check for GVT-g, it currently depends on intercepting CSB mmio v5: Fixup GVT-g mmio path v6: Disable HWSP if VT-d is active as the iommu adds unpredictable memory latency. (Mika) v7: Also markup the CSB read with READ_ONCE() as it may still be an mmio read and we want to stop the compiler from issuing a later (v.slow) reload. Suggested-by: Ben Widawsky <benjamin.widawsky@intel.com> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Michel Thierry <michel.thierry@intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Mika Kuoppala <mika.kuoppala@intel.com> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: Zhi Wang <zhi.a.wang@intel.com> Acked-by: Michel Thierry <michel.thierry@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20170913133534.26927-1-chris@chris-wilson.co.uk Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com> |
||
|---|---|---|
| .. | ||
| drm | ||
| host1x | ||
| ipu-v3 | ||
| vga | ||
| Makefile | ||