kmem_cache not showing in /proc/slabinfo

Hi All, I played a little bit around with kmem_cache_alloc() and kmem_cache_create() and figured out that it only appears in /proc/slabinfo if I reserve a specific amount of memory. Isn't it always preferable to precache space for often used structs even for small structs? I'm not sure whether I understood it right how it works. But how does the kernel know for how many structs he should preallocate memory? Best regards Jannik Becher