[dpdk-users] Should ''shmget" not be used to consume hugepages in DPDK?

[Stephen Hemminger]

On Fri, 20 Dec 2019 01:23:50 +0900
Byonggon Chun <byonggonchun at gmail.com> wrote:

> Hi all.
> I'm Kubernetes contributors and I'm working to make container isolation of
> hugepages that allows us to set hugepages limit per container cgroup.
> (At this point, limits are set on pod level cgroup even though we asked
> hugepages as the container level resource)
> 
> I tore down testPMD and some parts of DPDK lib and I got a question after i
> found there is no usage of "shmget" in DPDK.
> 
> My question is that Should "shmget" not be used to consume hugepages in
> DPDK?
> And here is following questions:
> 1) If we don't have to use "shmget", Why? Does it affect performance?
> 2) If I use "shmget" to get hugepages, should I call "mlock" syscall for it?
> 
> For more details, as I know there are three ways to consume hugepages in
> kubernetes.
> 1) shmget with SHM_HUGETLB
> 2) mmap with hugetlbs filebacking
> 3) mmap with MAP_ANONYMOUS | MAP_HUGETLB
> 
> And I found that testPMD calls mlock syscall when it maps an anonymous
> hugepages or external allocated hugepages.
> https://github.com/DPDK/dpdk/blob/924e55fb340623f03fdf2ff7fbcfd78819d1db25/app/test-pmd/testpmd.c#L896
> https://github.com/DPDK/dpdk/blob/924e55fb340623f03fdf2ff7fbcfd78819d1db25/app/test-pmd/testpmd.c#L916
> 
> Thanks.

shmget is a legacy Unix API and there is no point in using it.
For new applications libhugetlbfs is preferable.