[Intel-gfx] [PATCH 1/5] Revert "drm/i915/gt: Wait for new requests in intel_gt_retire_requests()"

[Joonas Lahtinen]

Quoting Chris Wilson (2019-11-21 09:10:40)
> From inside an active timeline in the execbuf ioctl, we may try to
> reclaim some space in the GGTT. We need GGTT space for all objects on
> !full-ppgtt platforms, and for context images everywhere. However, to
> free up space in the GGTT we may need to remove some pinned objects
> (e.g. context images) that require flushing the idle barriers to remove.
> For this we use the big hammer of intel_gt_wait_for_idle()
> 
> However, commit 7936a22dd466 ("drm/i915/gt: Wait for new requests in
> intel_gt_retire_requests()") will continue spinning on the wait if a
> timeline is active but lacks requests, as is the case during execbuf
> reservation. Spinning forever is quite time consuming, so revert that
> commit and start again.
> 
> In practice, the effect commit 7936a22dd466 was trying to achieve is
> accomplished by commit 1683d24c1470 ("drm/i915/gt: Move new timelines
> to the end of active_list"), so there is no immediate rush to replace
> the looping.
> 
> Testcase: igt/gem_exec_reloc/basic-range
> Fixes: 7936a22dd466 ("drm/i915/gt: Wait for new requests in intel_gt_retire_requests()")
> References: 1683d24c1470 ("drm/i915/gt: Move new timelines to the end of active_list")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Regards, Joonas