Re: [PATCH] SLAB - have index_of bug at compile time.

[Manfred Spraul <manfred@colorfullife.com>]

Pekka Enberg wrote:

>Hi Steven,
>
>On 12/26/05, Steven Rostedt <rostedt@goodmis.org> wrote:
>  
>
>>Now, maybe NUMA and vmalloc might be a good reason to start a new
>>allocation system along side of slab?
>>    
>>
>
>A better approach would probably be to introduce a vmem layer similar
>to what Solaris has to solve I/O memory and vmalloc issue. What NUMA
>issue are you referring to btw? I don't see any problem with the
>current design (in fact, I stole it for my magazine allocator too).
>It's just that the current implementation is bit hard to understand.
>
>  
>
This is virt_to_page() on i386: the object address is in %esi
     lea    0x40000000(%esi),%eax
     mov    0x0,%edx [0x0 is actually mem_map]
     shr    $0xc,%eax
     shl    $0x5,%eax
Just read the mem_map pointer and a few calculations.
And now retrieve the cachep pointer:
    mov    0x18(%eax,%edx,1),%edx

With NUMA on i386 (GENERIC_ARCH)
    lea    0x40000000(%edi),%eax
    mov    %eax,%ebx
    shr    $0x1c,%eax
    movsbl 0x0(%eax),%eax [ 0x0 is physnode_map]
    shr    $0xc,%ebx
    mov    0x0(,%eax,4),%ecx [0x0 is node_data]
    mov    %ebx,%eax
    mov    0xaa0(%ecx),%edx
    sub    %edx,%eax
    mov    0xa98(%ecx),%edx
    shl    $0x5,%eax
4 memory accesses.
    mov    0x18(%eax,%edx,1),%ebp

--
    Manfred