Re: [PATCH 05/12] mm, slub: lower the default slub_max_order with CONFIG_SLUB_TINY

[Hyeonggon Yoo]

On Mon, Nov 21, 2022 at 06:11:55PM +0100, Vlastimil Babka wrote:
> With CONFIG_SLUB_TINY we want to minimize memory overhead. By lowering
> the default slub_max_order we can make slab allocations use smaller
> pages. However depending on object sizes, order-0 might not be the best
> due to increased fragmentation. When testing on a 8MB RAM k210 system by
> Damien Le Moal [1], slub_max_order=1 had the best results, so use that
> as the default for CONFIG_SLUB_TINY.
> 
> [1] https://lore.kernel.org/all/6a1883c4-4c3f-545a-90e8-2cd805bcf4ae@xxxxxxxxxxxxxxxxxx/
> 
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
>  mm/slub.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 917b79278bad..bf726dd00f7d 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3888,7 +3888,8 @@ EXPORT_SYMBOL(kmem_cache_alloc_bulk);
>   * take the list_lock.
>   */
>  static unsigned int slub_min_order;
> -static unsigned int slub_max_order = PAGE_ALLOC_COSTLY_ORDER;
> +static unsigned int slub_max_order =
> +	IS_ENABLED(CONFIG_SLUB_TINY) ? 1 : PAGE_ALLOC_COSTLY_ORDER;
>  static unsigned int slub_min_objects;
>  
>  /*
> -- 
> 2.38.1
>

Reviewed-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>

-- 
Thanks,
Hyeonggon