about kmalloc and kmem_cache_alloc

[kernel.niko]

hi,everyone,
I'm wandering how to use kmalloc and kmem_cache_alloc.
as i know,kmalloc is based on kmem_cache_alloc ,so what's the different? when 
to use kmalloc? and
in what occasion,kmem_cache_alloc should be used? 
thanks.

2010-11-05 



kernel.niko