linux-kernel - Re: [PATCH v2 3/3] drm/i915/shrinker: Hook up vmap allocation failure notifier

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Date:	Tue, 05 Apr 2016 11:19:38 +0300
From:	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
To:	Chris Wilson <chris@...is-wilson.co.uk>,
	intel-gfx@...ts.freedesktop.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Roman Pen <r.peniaev@...il.com>,
	Mel Gorman <mgorman@...hsingularity.net>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
	Mika Kahola <mika.kahola@...el.com>
Subject: Re: [PATCH v2 3/3] drm/i915/shrinker: Hook up vmap allocation
 failure notifier

On ma, 2016-04-04 at 14:46 +0100, Chris Wilson wrote:
> If the core runs out of vmap address space, it will call a notifier in
> case any driver can reap some of its vmaps. As i915.ko is possibily
> holding onto vmap address space that could be recovered, hook into the
> notifier chain and try and reap objects holding onto vmaps.
> 
> Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Roman Pen <r.peniaev@...il.com>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Cc: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>

A comment below. But regardless;

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>

> Cc: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
> Cc: Mika Kahola <mika.kahola@...el.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h          |  1 +
>  drivers/gpu/drm/i915/i915_gem_shrinker.c | 39 ++++++++++++++++++++++++++++++++
>  2 files changed, 40 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index dd187727c813..6443745d4182 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1257,6 +1257,7 @@ struct i915_gem_mm {
>  	struct i915_hw_ppgtt *aliasing_ppgtt;
>  
>  	struct notifier_block oom_notifier;
> +	struct notifier_block vmap_notifier;
>  	struct shrinker shrinker;
>  	bool shrinker_no_lock_stealing;
>  
> diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> index e391ee3ec486..be7501afb59e 100644
> --- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
> +++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> @@ -28,6 +28,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>  #include 
>  
> @@ -356,6 +357,40 @@ i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
>  	return NOTIFY_DONE;
>  }
>  
> +static int
> +i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
> +{
> +	struct drm_i915_private *dev_priv =
> +		container_of(nb, struct drm_i915_private, mm.vmap_notifier);
> +	struct drm_device *dev = dev_priv->dev;
> +	unsigned long timeout = msecs_to_jiffies(5000) + 1;
> +	unsigned long freed_pages;
> +	bool was_interruptible;
> +	bool unlock;
> +
> +	while (!i915_gem_shrinker_lock(dev, &unlock) && --timeout) {
> +		schedule_timeout_killable(1);
> +		if (fatal_signal_pending(current))
> +			return NOTIFY_DONE;
> +	}
> +	if (timeout == 0) {
> +		pr_err("Unable to purge GPU vmaps due to lock contention.\n");
> +		return NOTIFY_DONE;
> +	}
> +
> +	was_interruptible = dev_priv->mm.interruptible;
> +	dev_priv->mm.interruptible = false;
> +
> +	freed_pages = i915_gem_shrink_all(dev_priv);
> +
> +	dev_priv->mm.interruptible = was_interruptible;

Up until here this is same function as the oom shrinker, so I would
combine these two and here do "if (vmap) goto out;" sort of thing.

Would just need a way to distinct between two calling sites. I did not
come up with a quick solution as both are passing 0 as event.

Regards, Joonas

> +	if (unlock)
> +		mutex_unlock(&dev->struct_mutex);
> +
> +	*(unsigned long *)ptr += freed_pages;
> +	return NOTIFY_DONE;
> +}
> +
>  /**
>   * i915_gem_shrinker_init - Initialize i915 shrinker
>   * @dev_priv: i915 device
> @@ -371,6 +406,9 @@ void i915_gem_shrinker_init(struct drm_i915_private *dev_priv)
>  
>  	dev_priv->mm.oom_notifier.notifier_call = i915_gem_shrinker_oom;
>  	WARN_ON(register_oom_notifier(&dev_priv->mm.oom_notifier));
> +
> +	dev_priv->mm.vmap_notifier.notifier_call = i915_gem_shrinker_vmap;
> +	WARN_ON(register_vmap_purge_notifier(&dev_priv->mm.vmap_notifier));
>  }
>  
>  /**
> @@ -381,6 +419,7 @@ void i915_gem_shrinker_init(struct drm_i915_private *dev_priv)
>   */
>  void i915_gem_shrinker_cleanup(struct drm_i915_private *dev_priv)
>  {
> +	WARN_ON(unregister_vmap_purge_notifier(&dev_priv->mm.vmap_notifier));
>  	WARN_ON(unregister_oom_notifier(&dev_priv->mm.oom_notifier));
>  	unregister_shrinker(&dev_priv->mm.shrinker);
>  }
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation