On 09/08/23 at 04:53pm, Vlastimil Babka wrote:
> After the previous cleanups, we can now move some code from
> calc_slab_order() to calculate_order() so it's executed just once, and
> do some more cleanups.
>
> - move the min_order and MAX_OBJS_PER_PAGE evaluation to
> calc_slab_order().
>
> - change calc_slab_order() parameter min_objects to min_order
>
> Also make MAX_OBJS_PER_PAGE check more robust by considering also
> min_objects in addition to slub_min_order. Otherwise this is not a
> functional change.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/slub.c | 19 +++++++++----------
> 1 file changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index f04eb029d85a..1c91f72c7239 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -4110,17 +4110,12 @@ static unsigned int slub_min_objects;
> * the smallest order which will fit the object.
> */
> static inline unsigned int calc_slab_order(unsigned int size,
> - unsigned int min_objects, unsigned int max_order,
> + unsigned int min_order, unsigned int max_order,
> unsigned int fract_leftover)
> {
> - unsigned int min_order = slub_min_order;
> unsigned int order;
>
> - if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE)
> - return get_order(size * MAX_OBJS_PER_PAGE) - 1;
> -
> - for (order = max(min_order, (unsigned int)get_order(min_objects * size));
> - order <= max_order; order++) {
> + for (order = min_order; order <= max_order; order++) {
>
> unsigned int slab_size = (unsigned int)PAGE_SIZE << order;
> unsigned int rem;
> @@ -4139,7 +4134,7 @@ static inline int calculate_order(unsigned int size)
> unsigned int order;
> unsigned int min_objects;
> unsigned int max_objects;
> - unsigned int nr_cpus;
> + unsigned int min_order;
>
> min_objects = slub_min_objects;
> if (!min_objects) {
> @@ -4152,7 +4147,7 @@ static inline int calculate_order(unsigned int size)
> * order on systems that appear larger than they are, and too
> * low order on systems that appear smaller than they are.
> */
> - nr_cpus = num_present_cpus();
> + unsigned int nr_cpus = num_present_cpus();
> if (nr_cpus <= 1)
> nr_cpus = nr_cpu_ids;
> min_objects = 4 * (fls(nr_cpus) + 1);
A minor concern, should we change 'min_objects' to be a local static
to avoid the "if (!min_objects) {" code block every time? It's deducing
the value from nr_cpus, we may not need do the calculation each time.
> @@ -4160,6 +4155,10 @@ static inline int calculate_order(unsigned int size)
> max_objects = order_objects(slub_max_order, size);
> min_objects = min(min_objects, max_objects);
>
> + min_order = max(slub_min_order, (unsigned int)get_order(min_objects * size));
> + if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE)
> + return get_order(size * MAX_OBJS_PER_PAGE) - 1;
> +
> /*
> * Attempt to find best configuration for a slab. This works by first
> * attempting to generate a layout with the best possible configuration and
> @@ -4176,7 +4175,7 @@ static inline int calculate_order(unsigned int size)
> * long as at least single object fits within slub_max_order.
> */
> for (unsigned int fraction = 16; fraction > 1; fraction /= 2) {
> - order = calc_slab_order(size, min_objects, slub_max_order,
> + order = calc_slab_order(size, min_order, slub_max_order,
> fraction);
> if (order <= slub_max_order)
> return order;
> --
> 2.42.0
>
