mm/slub: make the description of slab_min_objects helpful in doc

There is no a value assigned to slab_min_objects by default, it always
is 0 that is initialized by compiler if no assigned value by command line.
min_objects is calculated based on processor numbers in calculate_order().
For more details, see commit 9b2cd506 ("slub: Calculate min_objects
based on number of processors.")
Signed-off-by: Xiongwei Song <xiongwei.song@windriver.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Documentation/mm/slub.rst

@@ -150,7 +150,7 @@ list_lock once in a while to deal with partial slabs. That overhead is
 governed by the order of the allocation for each slab. The allocations
 can be influenced by kernel parameters:
 
-.. slab_min_objects=x		(default 4)
+.. slab_min_objects=x		(default: automatically scaled by number of cpus)
 .. slab_min_order=x		(default 0)
 .. slab_max_order=x		(default 3 (PAGE_ALLOC_COSTLY_ORDER))