kernel memory

[Petri Helenius]

Peter Wemm wrote:

>
>AARGH.  I've just found a bug/feature in the memory allocator.
>
>There are two code paths, one for small (<PAGE_SIZE) allocations, which 
>uses the direct map allocations instead of kvm allocations, and the 
>other large chunk allocator that simply allocates pages at a time from 
>kvm. :-(
>
>I suspect this is because malloc's semantics depend on objects being 
>contiguous. The direct map method would allocate physically 
>discontiguous pages.
>
>So, if you allocated your lookup cache in <4K chunks, you could have as 
>much as you like. :-/
>  
>
Is there an overhead I should be aware of if I say allocate 10 million 
400 byte entries? (other than I obviously suffer the overhead of keeping 
an array of pointers)

Pete