On Fri, 17 Aug 2012, Hanjun Guo wrote:
> N_NORMAL_MEMORY means non-LRU page allocs possible.
Hmmm... It may be better to say
N_NORMAL_MEMORY Allocations are allowed for pages that will not be
managed via a LRU and that cannot be moved by the page migration logic.
N_LRU_MEMORY Allocations are possible for pages that are managed via LRUs
N_HIGH_MEMORY Allocations are allowed for pages that are only temporarliy mapped into kernel address space.
Any node that has the ability to allocate memory at all has at least N_LRU_MEMORY set.
>
> /*
> * Bitmasks that are kept for all the nodes.
> + * N_NORMAL_MEMORY means non-LRU page allocs possible.
> + * N_LRU_MEMORY means LRU page 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,
> + * node with ZONE_HIGHMEM is marked with N_LRU_MEMORY and N_HIGH_MEMORY.
> + * N_LRU_MEMORY also means node has any regular memory.
> */
> enum node_states {
> N_POSSIBLE, /* The node could become online at some point */
> N_ONLINE, /* The node is online */
> - N_NORMAL_MEMORY, /* The node has regular memory */
> + N_NORMAL_MEMORY, /* The node has normal memory */
> + N_LRU_MEMORY, /* The node has regular memory */
These comments are utter garbage and just repeat what the constant
alreadty expresses. . Please actually say something meaningful that
another developer can use when he attempts to understand what these bits
mean.
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