Hi Vlastimil,
On Fri, Sep 08, 2023 at 10:53:04PM +0800, Vlastimil Babka wrote:
> If calculate_order() can't fit even a single large object within
> slub_max_order, it will try using the smallest necessary order that may
> exceed slub_max_order but not MAX_ORDER.
>
> Currently this is done with a call to calc_slab_order() which is
> unecessary. We can simply use get_order(size). No functional change.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/slub.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index f7940048138c..c6e694cb17b9 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -4193,7 +4193,7 @@ static inline int calculate_order(unsigned int size)
> /*
> * Doh this slab cannot be placed using slub_max_order.
> */
> - order = calc_slab_order(size, 1, MAX_ORDER, 1);
> + order = get_order(size);
This patchset is a nice cleanup, and my previous test all looked fine.
And one 'slub_min_order' setup reminded by Christopher [1] doesn't
work as not taking affect with this 1/4 patch.
The root cause seems to be, in current kernel, the 'slub_max_order'
is not ajusted accordingly with 'slub_min_order', so there is case
that 'slub_min_order' is bigger than the default 'slub_max_order' (3).
And it could be fixed by the below patch
diff --git a/mm/slub.c b/mm/slub.c
index 1c91f72c7239..dbe950783105 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4702,6 +4702,9 @@ static int __init setup_slub_min_order(char *str)
{
get_option(&str, (int *)&slub_min_order);
+ if (slub_min_order > slub_max_order)
+ slub_max_order = slub_min_order;
+
return 1;
}
Though the formal fix may also need to cover case like this kind of
crazy setting "slub_min_order=6 slub_max_order=5"
[1]. https://lore.kernel.org/lkml/21a0ba8b-bf05-0799-7c78-2a35f8c8d52a@xxxxxxxxxxxxxxxxxxxxxx/
Thanks,
Feng
> if (order <= MAX_ORDER)
> return order;
> return -ENOSYS;
> --
> 2.42.0
>
>
