[Devel] Re: [PATCH 1/4] Add notification about some major slab events

[Christoph Lameter]

On Mon, 17 Sep 2007, Pavel Emelyanov wrote:

> @@ -1036,7 +1121,10 @@ static struct page *allocate_slab(struct
>  		page = alloc_pages_node(node, flags, s->order);
>  
>  	if (!page)
> -		return NULL;
> +		goto out;
> +
> +	if (slub_newpage_notify(s, page, flags) < 0)
> +		goto out_free;
>  
>  	mod_zone_page_state(page_zone(page),
>  		(s->flags & SLAB_RECLAIM_ACCOUNT) ?
> @@ -1044,6 +1132,11 @@ static struct page *allocate_slab(struct
>  		pages);
>  
>  	return page;
> +
> +out_free:
> +	__free_pages(page, s->order);
> +out:
> +	return NULL;
>  }

Ok that looks sane.

>  static void setup_object(struct kmem_cache *s, struct page *page,
> @@ -1136,6 +1229,8 @@ static void rcu_free_slab(struct rcu_hea
>  
>  static void free_slab(struct kmem_cache *s, struct page *page)
>  {
> +	slub_freepage_notify(s, page);
> +
>  	if (unlikely(s->flags & SLAB_DESTROY_BY_RCU)) {
>  		/*
>  		 * RCU free overloads the RCU head over the LRU

Ditto.

> @@ -1555,6 +1650,11 @@ static void __always_inline *slab_alloc(
>  	}
>  	local_irq_restore(flags);
>  
> +	if (object && slub_alloc_notify(s, object, gfpflags) < 0) {
> +		kmem_cache_free(s, object);
> +		return NULL;
> +	}
> +
>  	if (unlikely((gfpflags & __GFP_ZERO) && object))
>  		memset(object, 0, c->objsize);
>  

Please stay completely out of the fast path. No modifications to 
slab_alloc or slab_free please. It is possible to force all allocations of 
a particular slab of interest to use the slow path in __slab_alloc (maybe 
as a result of the slab page allocation hook returning a certain result 
code). See how the SLAB_DEBUG handling does it. You can adapt that and then do the 
object checks in __slab_alloc.