Re: [RFC PATCH] mm: introduce N_LRU_MEMORY to distinguish between normal and movable memory

[Hanjun Guo <guohanjun@huawei.com>]

On 2012/8/10 22:12, Christoph Lameter (Open Source) wrote:
> On Fri, 10 Aug 2012, Hanjun Guo wrote:
> 
>> On 2012/8/9 22:06, Christoph Lameter (Open Source) wrote:
>>> On Thu, 9 Aug 2012, Hanjun Guo wrote:
>>>
>>>> Now, We have node masks for both N_NORMAL_MEMORY and
>>>> N_HIGH_MEMORY to distinguish between normal and highmem on platforms such as x86.
>>>> But we still don't have such a mechanism to distinguish between "normal" and "movable"
>>>> memory.
>>>
>>> What is the exact difference that you want to establish?
>>
>> Hi Christoph,
>>     Thanks for your comments very much!
>>
>> We want to identify the node only has ZONE_MOVABLE memory.
>> for example:
>> 	node 0: ZONE_DMA, ZONE_DMA32, ZONE_NORMAL--> N_LRU_MEMORY, N_NORMAL_MEMORY
>> 	node 1: ZONE_MOVABLE			 --> N_LRU_MEMORY
>> thus, in SLUB allocator, will not allocate memory control structures for node1.
> 
> So this would change the N_NORMAL_MEMORY definition so that N_NORMAL
> means !LRU allocs possible? So far N_NORMAL_MEMORY has a wider scope of
> meaning. We need an accurate definition of the meaning of all these
> attributes.

Hi Christoph,
Sorry for the late reply.

yes, N_LRU_MEMORY means LRU allocs possible,
N_NORMAL_MEMORY means !LRU allocs possible.
node with ZONE_DMA/ZONE_DMA32/ZONE_NORMAL is marked with N_LRU_MEMORY and N_NORMAL_MEMORY,
node with ZONE_MOVABLE is *only* marked with N_LRU_MEMORY.

> 
>>> For the slab case that you want to solve here you will need to know if the
>>> node has *only* movable memory and will never have any ZONE_NORMAL memory.
>>> If so then memory control structures for allocators that do not allow
>>> movable memory will not need to be allocated for these node. The node can
>>> be excluded from handling.
>>
>> I think this is what we are trying to do in this patch.
>> did I miss something?
> 
> THe meaning of ZONE_NORMAL seems to change which causes confusion. Please
> describe in detail what each of these attributes mean.
> 
> .
> 


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