Re: The limitation of VHOST_MEMORY_MAX_NREGIONS in virtio-user with vhost-user backend

[Yuanhan Liu <yliu@fridaylinux.org>]

On Wed, Dec 06, 2017 at 12:23:19PM +0100, Maxime Coquelin wrote:
> Hi,
> 
> 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.

He was talking about virtio-user.

	--yliu
> 
> 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...)?
> 
> Cheers,
> Maxime
> >
> >
> >Vivian
> >seat:      19009
> >phone: 13738006921
> >
> >
> >