Re: [patch 8/8] slub: Make the order configurable for each slab cache

[Pekka Enberg <penberg@cs.helsinki.fi>]

Hi Christoph,

Christoph Lameter wrote:
> Makes /sys/kernel/slab/<slabname>/order writable. The allocation
> order can then be changed dynamically during runtime.
> 
> Signed-off-by: Christoph Lameter <clameter@sgi.com>
> 
> ---
>  mm/slub.c |   17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> +static ssize_t order_store(struct kmem_cache *s,
> +				const char *buf, size_t length)
> +{
> +	int order = simple_strtoul(buf, NULL, 10);
> +
> +	if (order > slub_max_order)
> +		return -EINVAL;
> +
> +	s->order = order;
> +	calculate_sizes(s);
> +	return length;

I think we need to respect slub_min_order here as well and most 
importantly, check whether cache size allows the given order; otherwise 
calculate_sizes can end up with -1 set to s->order which makes the cache 
useless (and probably makes SLUB oops).

			Pekka

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