Re: [PATCH] drm/i915: During shrink_all we only need to idle the GPU

Daniel Vetter
2015-06-29T07:11:14Z

On Sun, Jun 28, 2015 at 01:06:39PM +0100, Chris Wilson wrote:
> We can forgo an evict-everything here as the shrinker operation itself
> will unbind any vma as required. If we explicitly idle the GPU through a
> switch to the default context, we not only create a request in an
> illegal context (e.g. whilst shrinking during execbuf with a request
> already allocated), but switching to the default context will not free
> up the memory backing the active contexts - unless in the unlikely
> situation that context had already been closed (and just kept arrive by
> being the current context). The saving is near zero and the danger real.

Has this already blown up in some bugzilla somewhere? Should be a fairly
recent regression with the olr removal.

> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
> drivers/gpu/drm/i915/i915_gem_shrinker.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> index c41ddf92e404..2d8c79b8c378 100644
> --- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
> +++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> @@ -158,9 +158,16 @@ i915_gem_shrink(struct drm_i915_private *dev_priv,
> */
> unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv)
> {
> - i915_gem_evict_everything(dev_priv->dev);
> - return i915_gem_shrink(dev_priv, LONG_MAX,
> - I915_SHRINK_BOUND | I915_SHRINK_UNBOUND);
> + unsigned long count;
> +
> + count = i915_gem_shrink(dev_priv, LONG_MAX,
> + I915_SHRINK_BOUND | I915_SHRINK_UNBOUND);
> +
> + /* Use a double call to retire to flush any staged frees */
> + i915_gem_retire_requests(dev_priv->dev);
> + i915_gem_retire_requests(dev_priv->dev);

I'm lost - where's that staged free?
-Daniel

> +
> + return count;
> }
>
> static bool i915_gem_shrinker_lock(struct drm_device *dev, bool *unlock)
> --
> 2.1.4
>
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--
Daniel Vetter
Software Engineer, Intel Corporation