[Intel-gfx] [PATCH v4 2/3] drm/i915: refactor duplicate object vmap functions (reworked)
Tvrtko Ursulin
tvrtko.ursulin at linux.intel.com
Tue Feb 23 12:25:29 UTC 2016
On 23/02/16 11:52, Chris Wilson wrote:
> On Tue, Feb 23, 2016 at 11:38:02AM +0000, Chris Wilson wrote:
>> Indeed, we would need a new notifier, pretty much for the sole use of
>> 32b. Grr, that will be a nuisance.
>
> Core changes:
>
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index d1f1d338af20..542a91c2785f 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -187,4 +187,8 @@ pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
> #define VMALLOC_TOTAL 0UL
> #endif
>
> +struct notitifer_block;
> +int register_vmap_notifier(struct notifier_block *nb);
> +int unregister_vmap_notifier(struct notifier_block *nb);
> +
> #endif /* _LINUX_VMALLOC_H */
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index fb42a5bffe47..0735d82444f7 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -21,6 +21,7 @@
> #include <linux/debugobjects.h>
> #include <linux/kallsyms.h>
> #include <linux/list.h>
> +#include <linux/notifier.h>
> #include <linux/rbtree.h>
> #include <linux/radix-tree.h>
> #include <linux/rcupdate.h>
> @@ -344,6 +345,8 @@ static void __insert_vmap_area(struct vmap_area *va)
>
> static void purge_vmap_area_lazy(void);
>
> +static BLOCKING_NOTIFIER_HEAD(vmap_notify_list);
> +
> /*
> * Allocate a region of KVA of the specified size and alignment, within the
> * vstart and vend.
> @@ -356,6 +359,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> struct vmap_area *va;
> struct rb_node *n;
> unsigned long addr;
> + unsigned long freed;
> int purged = 0;
> struct vmap_area *first;
>
> @@ -468,6 +472,12 @@ overflow:
> purged = 1;
> goto retry;
> }
> + freed = 0;
> + blocking_notifier_call_chain(&vmap_notify_list, 0, &freed);
> + if (freed > 0) {
> + purged = 0;
> + goto retry;
> + }
> if (printk_ratelimit())
> pr_warn("vmap allocation for size %lu failed: "
> "use vmalloc=<size> to increase size.\n", size);
> @@ -475,6 +485,18 @@ overflow:
> return ERR_PTR(-EBUSY);
> }
>
> +int register_vmap_notifier(struct notifier_block *nb)
> +{
> + return blocking_notifier_chain_register(&vmap_notify_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(register_vmap_notifier);
> +
> +int unregister_vmap_notifier(struct notifier_block *nb)
> +{
> + return blocking_notifier_chain_unregister(&vmap_notify_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(unregister_vmap_notifier);
> +
> static void __free_vmap_area(struct vmap_area *va)
> {
> BUG_ON(RB_EMPTY_NODE(&va->rb_node));
>
>
> That doesn't look too horrendous. Names?
Downside is new deadlock opportunity so GEM callers to vmap would have
to release the struct mutex.
> register_oovmap_notifier
> register_vmap_nospace_notifier?
> register_vmap_purge_notifier?
register_vmap_shrinker ?
> And the 64k question, how to sell it?
Not sure, maybe with numbers showing that caching the vmapping helps us
significantly?
Regards,
Tvrtko
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