[Intel-gfx] [PATCH v2] drm/i915: Idle the GPU before shinking everything

[Joonas Lahtinen]

On Wed, 2017-11-08 at 09:44 +0000, Chris Wilson wrote:
> The handling of contexts are peculiar. Instead of tieing their vma to
> activity, we pin the context. This means that we cannot simply unbind
> the context object itself at will (which would normally cause us to wait
> for the vma to be idle), but must manually idle the GPU and retire
> requests first.
> 
> A consequence of this peculiarity is when doing a last desperate attempt
> to recover memory. If the memory is tied up inside active context
> objects, we will fail to recover any memory simply by trying to unbind
> the objects without first doing a wait-for-idle.
> 
> A side-effect of removing the call to shrinker_lock_uninterruptible()
> from i915_gem_shrinker_oom() was that we removed an unlocked
> wait-for-idle, and so lost the "natural" shrinkage of context objects.
> By replacing that with a locked wait from inside i915_gem_shrink(), we
> not only replace it with the ability to recover all context objects, but
> do so for all i915_gem_shrink_all() callers.
> 
> v2: Switching requires request allocation, which is not permitted from
> inside the shrinker as it only uses ordinary allocations.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=102936
> Fixes: f2123818ffad ("drm/i915: Move dev_priv->mm.[un]bound_list to its own lock")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

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

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation