[dpdk-dev] Memory allocation in dpdk at basic level

[Burakov, Anatoly]

On 22-Oct-18 10:08 PM, Avinash Chaurasia wrote:
> Hello,
> I am not sure whether this is right list for posting this problem. I am
> trying to understand how dpdk allocate memory. I tried digging code to
> understand memory allocation of DPDK. So far I understood that memory is
> allocated from a heap that dpdk maintains. However, this heap must be
> allocated at some place. I failed to traceback any function (called from
> heap_alloc()) that calls mmap to allocate memory. Please let me know when
> this heap is created, which function call does that.
> Thanks
> Avinash
> 

Hi Avinash,

Here's a very high level overview.

At initialization, we mmap() anonymous memory regions (eal_memory.c 
contains the code - both for legacy and non-legacy mode). Then, we map 
actual pages into that space either at init (in legacy mode) or as 
needed (in non-legacy mode).

In legacy mode, pages are mapped into anonymous memory straight away 
(see legacy init code in eal_memory.c). For non-legacy, page allocation 
happens in eal_memalloc.c on request from malloc (see malloc_heap.c). In 
both cases, newly allocated pages are added to DPDK heap, and from there 
they can be used by the rest of DPDK using rte_malloc or 
rte_memzone_reserve API's.

-- 
Thanks,
Anatoly