[dpdk-dev] The limitation of VHOST_MEMORY_MAX_NREGIONS in virtio-user with vhost-user backend

Maxime Coquelin maxime.coquelin at redhat.com
Wed Dec 6 12:23:19 CET 2017


On 12/05/2017 07:58 AM, Wang, Wei 5. (NSB - CN/Hangzhou) wrote:
> Hi, all
> In DPDK document, it it described that Virtio in containers Cannot work when there are more than VHOST_MEMORY_MAX_NREGIONS(8) hugepages. In another word, do not use 2MB hugepage so far. Do you know the reason of this limitation?

What document are you referring to?
Actually, a single region is composed of several hugepages, be it 1G or
2M. I use 2M hugepages daily without issues.

The limitation comes from the Vhost-user protocol spec. I know there are
discussions to enlarge it, but it would require a new protocol flag not
to break existing implementations, so no workaround possible.

> In my envirionment, the pdpe1gb is not set in cpu flag, so hugepage can't be set to 1GB size. The hugepage number shall be more than 8
> So is there any solution or workaround to fix this limitation? Or change dpdk code to fix this limitation?

Have you tried to use 2MB pages and faced the NREGIONS > 8 case?
If so, could you tell us more about your setup (QEMU version, VM RAM
size, etc...)?

> Vivian
> seat:      19009
> phone: 13738006921

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