Re: [PATCH 3/3] drm/i915: Allocate active tracking nodes from a slabcache

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 30/01/2019 20:50, Chris Wilson wrote:
> Wrap the active tracking for a GPU references in a slabcache for faster
> allocations, and hopefully better fragmentation reduction.
>

v2 where art thou? :)

> v3: Nothing device specific left, it's just a slabcache that we can
> make global.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/i915_active.c | 31 +++++++++++++++++++++++++++---
>   drivers/gpu/drm/i915/i915_active.h |  3 +++
>   drivers/gpu/drm/i915/i915_pci.c    |  3 +++
>   3 files changed, 34 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
> index b1fefe98f9a6..5818ddf88462 100644
> --- a/drivers/gpu/drm/i915/i915_active.c
> +++ b/drivers/gpu/drm/i915/i915_active.c
> @@ -9,6 +9,17 @@
>   
>   #define BKL(ref) (&(ref)->i915->drm.struct_mutex)
>   
> +/*
> + * Active refs memory management
> + *
> + * To be more economical with memory, we reap all the i915_active trees as
> + * they idle (when we know the active requests are inactive) and allocate the
> + * nodes from a local slab cache to hopefully reduce the fragmentation.
> + */
> +static struct i915_global_active {
> +	struct kmem_cache *slab_cache;
> +} global;
> +
>   struct active_node {
>   	struct i915_gem_active base;
>   	struct i915_active *ref;
> @@ -23,7 +34,7 @@ __active_park(struct i915_active *ref)
>   
>   	rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
>   		GEM_BUG_ON(i915_gem_active_isset(&it->base));
> -		kfree(it);
> +		kmem_cache_free(global.slab_cache, it);
>   	}
>   	ref->tree = RB_ROOT;
>   }
> @@ -96,11 +107,11 @@ active_instance(struct i915_active *ref, u64 idx)
>   			p = &parent->rb_left;
>   	}
>   
> -	node = kmalloc(sizeof(*node), GFP_KERNEL);
> +	node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
>   
>   	/* kmalloc may retire the ref->last (thanks shrinker)! */
>   	if (unlikely(!i915_gem_active_raw(&ref->last, BKL(ref)))) {
> -		kfree(node);
> +		kmem_cache_free(global.slab_cache, node);
>   		goto out;
>   	}
>   
> @@ -234,6 +245,20 @@ void i915_active_fini(struct i915_active *ref)
>   	GEM_BUG_ON(!RB_EMPTY_ROOT(&ref->tree));
>   	GEM_BUG_ON(ref->count);
>   }
> +
> +int __init i915_global_active_init(void)
> +{
> +	global.slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN);
> +	if (!global.slab_cache)
> +		return -ENOMEM;
> +
> +	return 0;
> +}
> +
> +void __exit i915_global_active_exit(void)
> +{
> +	kmem_cache_destroy(global.slab_cache);
> +}
>   #endif
>   
>   #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
> diff --git a/drivers/gpu/drm/i915/i915_active.h b/drivers/gpu/drm/i915/i915_active.h
> index 6130c6770d10..48fdb1497883 100644
> --- a/drivers/gpu/drm/i915/i915_active.h
> +++ b/drivers/gpu/drm/i915/i915_active.h
> @@ -63,4 +63,7 @@ void i915_active_fini(struct i915_active *ref);
>   static inline void i915_active_fini(struct i915_active *ref) { }
>   #endif
>   
> +int i915_global_active_init(void);
> +void i915_global_active_exit(void);
> +
>   #endif /* _I915_ACTIVE_H_ */
> diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
> index 44c23ac60347..751a787c83d1 100644
> --- a/drivers/gpu/drm/i915/i915_pci.c
> +++ b/drivers/gpu/drm/i915/i915_pci.c

Add explicit #include "i915_active.h"?

> @@ -793,6 +793,8 @@ static int __init i915_init(void)
>   	bool use_kms = true;
>   	int err;
>   
> +	i915_global_active_init();
> +
>   	err = i915_mock_selftests();
>   	if (err)
>   		return err > 0 ? 0 : err;
> @@ -824,6 +826,7 @@ static void __exit i915_exit(void)
>   		return;
>   
>   	pci_unregister_driver(&i915_pci_driver);
> +	i915_global_active_exit();
>   }
>   
>   module_init(i915_init);
> 

Regards,

Tvrtko
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