[dpdk-dev] Is contiguous hugepages memory still required in latest DPDKs?

Ruslan Bilovol rbilovol at cisco.com
Wed Mar 22 13:08:38 CET 2017


On 03/21/2017 04:41 PM, Sergio Gonzalez Monroy wrote:
> The DPDK will still try to allocate contiguous hugepages.
> Since DPDK v16.07 the mempool library is able to create a mempool with multiple chunks of memory.
> You would still have the contig memory restriction for any other DPDK library or app.
>
> Are you pre-allocating hugepages on boot (kernel cmdline) or runtime?
I tried both cases, and there is no much difference between them.
(I used debug prints in kernel to see physical address of preallocated hugepages

Main issue is that linux kernel memory allocation algorithm was changed
with "fair zone allocator policy" commits, and in my case need to
pre-allocate 2x or even 3x more hugepages now.

Regards,
Ruslan

>
> Sergio
>
> On 21/03/2017 14:20, Ruslan Bilovol wrote:
>> Hi,
>>
>> Recently after moving to 4.4 Linux kernel we found that DPDK v16.07
>> can't find physically contiguous chunk of hugepages memory.
>>
>> I've tracked this down to kernel commits
>>  81c0a2bb515f ("mm: page_alloc: fair zone allocator policy")
>>  fff4068cba48 ("mm: page_alloc: revert NUMA aspect of fair allocation policy")
>>  4ffeaf3560a5 ("mm: page_alloc: reduce cost of the fair zone allocation policy")
>>
>> These commits changed default page allocator behavior so it now allocates
>> memory proportionally from preferred and lower zones. Hugepages
>> are scattered proportionally among few memory zones, so possibility
>> to find big physically contiguous chunk of hugepages memory is much lower.
>>
>> I see that there were some attempts to move from contiguous hugepages
>> approach, like http://dpdk.org/ml/archives/dev/2016-March/035201.html
>> Also some discussion here: http://dpdk.org/ml/archives/users/2016-October/001050.html
>>
>> The question: is contiguous hugepages memory still required in latest DPDKs,
>> and if not, since which version?
>>
>> Thanks,
>> Ruslan
>>
>



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