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* Qixuan Wu (qixuan.wu at linux.alibaba.com) wrote:
> Hi Stefan,

Hi,
  Stefan is out at the moment, so I thought I'd reply.

> Now we found 9pfs performance is poor, we are thinking of other solution
> for the rootfs of kata container.
> 
> As per the link, https://github.com/kata-containers/runtime/issues/279.
> Seem you are doing about nfs/vsock optimization, and nfs/vsock seems
> that can possible be the future default rootfs of kata container.
> 
> And I heard about qcow2+snapshot+virtio_scsi also. And how do you think
> about it as the rootfs of kata container? And do you know how the kata
> commumity think about this solution also and compare it with nfs/vsock ?

We're currently experimenting with something a bit different;
we've got a setup that uses a modified version of the FUSE protocol
running over vhost-user;  it's:
  a) Got the filesystem access split out of qemu into a separate daemon
      - that's just a modified version of a normal FUSE filesystem daemon
      with the nice bit being that since it's a separate process you
      can do whatever isolation on it you want.
  b) But the latency is low because vhost-user means the daemon can read
     the request queue straight out of the guest memory
  c) We've got a setup with DAX so that the files are mapped straight
     into guest address space, so the overhead is very low for large
     files.
  d) We've got a caching scheme for metadata, which again removes a lot
     of latency.
  e) We've got some patches to use it in KATA; I can start a basic KATA
     guest with it.

This is the first public mention of it because I didn't want you waiting
for a reply; but our code is still rather messy and experimental; give
us a few weeks and as soon as it survives some smoke tests we'll make
the code public.

Because we're reusing both FUSE and vhost-user the kernel changes are
quite small, as are the qemu changes.

I realise that's not much detail yet; we're starting to write some of it
up; feel free to ask any specifics.

Dave

> Anything is welcome and helpful.
> 
> Thanks & Regards
> Qixuan Wu.
> 
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--
Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK