Re: [RFC] Reimplementation of linux dynamic percpu memory allocator

[Manfred Spraul <manfred@colorfullife.com>]

Ravikiran G Thirumalai wrote:

>Hmmm..I knew from some experiments earlier that access to per cpu versions
>of memory was slow with the slab based implementation -- which this patch
>addresses, but I didn't know allocs themselves were slow...
>Creation of a disk should not be a fast path no?
>  
>
No, not fast path. But it can happen a few thousand times. The slab 
implementation failed due to heavy internal fragmentation. If your code 
runs fine with a few thousand users, then there shouldn't be a problem.

>>>      
>>>
>>That means no large pte entries for the per-cpu allocations, right?
>>I think that's a bad idea for non-numa systems. What about a fallback to 
>>simple getfreepages() for non-numa systems?
>>    
>>
>
>Can we have large pte entries with PAGE_SIZEd pages?  
>
>  
>
For non-NUMA systems, I would use get_free_pages() to allocate a 
multi-page area instead of map_vm_area(). Typically, get_free_pages() is 
backed by large pte memory and map_vm_area() by normal virtual memory.

--
    Manfred