Re: [dpdk-dev] rte_mempool_create fails with ENOMEM

[Alex Markuze <alex@weka.io>]

I've Also seen a similar issue when trying to run a dpdk app which
allocates huge pools(~0.5GB) after a memory heavy operation on the machine.

I've come to the same conclusion as you did, that internal fragmentation is
causing pool creation failures.
It seems that the rte_mempool_xmem_create/rte_memzone_reserve_aligned are
attempting to create physicaly contiguous pools. Which may offer a slight
performance gain(?) but may cause unpredictable allocation issues which is
a big risk for DC deployments where hundreds or even thousands of machines
may be deployed with a dpdk app and fail inexplicably.

I didn't really get the chance to digg into the memory managment internals
of DPDK, so feel free to correct me where I'm off.

Thanks.

On Thu, Dec 18, 2014 at 3:25 PM, Newman Poborsky <newman555p@gmail.com>
wrote:
>
> Hi,
>
> could someone please provide any explanation why sometimes mempool creation
> fails with ENOMEM?
>
> I run my test app several times without any problems and then I start
> getting ENOMEM error when creating mempool that are used for packets. I try
> to delete everything from /mnt/huge, I increase the number of huge pages,
> remount /mnt/huge but nothing helps.
>
> There is more than enough memory on server. I tried to debug
> rte_mempool_create() call and it seems that after server is restarted free
> mem segments are bigger than 2MB, but after running test app for several
> times, it seems that all free mem segments have a size of 2MB, and since I
> am requesting 8MB for my packet mempool, this fails.  I'm not really sure
> that this conclusion is correct.
>
> Does anybody have any idea what to check and how running my test app
> several times affects hugepages?
>
> For me, this doesn't make any since because after test app exits, resources
> should be freed, right?
>
> This has been driving me crazy for days now. I tried reading a bit more
> theory about hugepages, but didn't find out anything that could help me.
> Maybe it's something else and completely trivial, but I can't figure it
> out, so any help is appreciated.
>
> Thank you!
>
> BR,
> Newman P.
>