netdev - Re: [PATCH 4/7] slab: implement bulking for SLAB allocator

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Date:	Mon, 28 Sep 2015 10:11:09 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	netdev@...r.kernel.org,
	Alexander Duyck <alexander.duyck@...il.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH 4/7] slab: implement bulking for SLAB allocator

On Mon, 28 Sep 2015, Jesper Dangaard Brouer wrote:

> +/* Note that interrupts must be enabled when calling this function. */
>  bool kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
> -								void **p)
> +			   void **p)
>  {
> -	return __kmem_cache_alloc_bulk(s, flags, size, p);
> +	size_t i;
> +
> +	local_irq_disable();
> +	for (i = 0; i < size; i++) {
> +		void *x = p[i] = slab_alloc(s, flags, _RET_IP_, false);
> +
> +		if (!x) {
> +			__kmem_cache_free_bulk(s, i, p);
> +			return false;
> +		}
> +	}
> +	local_irq_enable();
> +	return true;
>  }
>  EXPORT_SYMBOL(kmem_cache_alloc_bulk);
>

Ok the above could result in excessive times when the interrupts are
kept off.  Lets say someone is freeing 1000 objects?

> +/* Note that interrupts must be enabled when calling this function. */
> +void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
> +{
> +	size_t i;
> +
> +	local_irq_disable();
> +	for (i = 0; i < size; i++)
> +		__kmem_cache_free(s, p[i], false);
> +	local_irq_enable();
> +}
> +EXPORT_SYMBOL(kmem_cache_free_bulk);

Same concern here. We may just have to accept this for now.

Acked-by: Christoph Lameter <cl@...ux.com>
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