Hi,
On Tue, Jun 17, 2014 at 10:09:52AM +0900, Joonsoo Kim wrote:
[...]
> To fix the problem, I introduces object status buffer on each slab.
> With this, we can track object status precisely, so slab leak detector
> would not access active object and no kernel oops would occur.
> Memory overhead caused by this fix is only imposed to
> CONFIG_DEBUG_SLAB_LEAK which is mainly used for debugging, so memory
> overhead isn't big problem.
[...]
>
> +static size_t calculate_freelist_size(int nr_objs, size_t align)
> +{
> + size_t freelist_size;
> +
> + freelist_size = nr_objs * sizeof(freelist_idx_t);
> + if (IS_ENABLED(CONFIG_DEBUG_SLAB_LEAK))
> + freelist_size += nr_objs * sizeof(char);
> +
> + if (align)
> + freelist_size = ALIGN(freelist_size, align);
> +
> + return freelist_size;
> +}
> +
> static int calculate_nr_objs(size_t slab_size, size_t buffer_size,
> size_t idx_size, size_t align)
> {
> int nr_objs;
> + size_t remained_size;
> size_t freelist_size;
> + int extra_space = 0;
>
> + if (IS_ENABLED(CONFIG_DEBUG_SLAB_LEAK))
> + extra_space = sizeof(char);
> /*
> * Ignore padding for the initial guess. The padding
> * is at most @align-1 bytes, and @buffer_size is at
> @@ -590,14 +641,15 @@ static int calculate_nr_objs(size_t slab_size, size_t buffer_size,
> * into the memory allocation when taking the padding
> * into account.
> */
> - nr_objs = slab_size / (buffer_size + idx_size);
> + nr_objs = slab_size / (buffer_size + idx_size + extra_space);
There is one more function that wants to know how much space per object
is spent for management. It's calculate_slab_order():
if (flags & CFLGS_OFF_SLAB) {
/*
* Max number of objs-per-slab for caches which
* use off-slab slabs. Needed to avoid a possible
* looping condition in cache_grow().
*/
offslab_limit = size;
offslab_limit /= sizeof(freelist_idx_t);
if (num > offslab_limit)
break;
}
May be, we should update it too?
Thanks.
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