Re: [libvirt PATCHv3 04/12] docs: add virtiofs kbase

On Thu, Jan 30, 2020 at 06:06:20PM +0100, Ján Tomko wrote: > Add a document describing the usage of virtiofs. > --- > docs/kbase.html.in | 3 + > docs/kbase/virtiofs.rst | 152 ++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 155 insertions(+) > create mode 100644 docs/kbase/virtiofs.rst > > diff --git a/docs/kbase.html.in b/docs/kbase.html.in > index c156414c41..7d6caf3cb1 100644 > --- a/docs/kbase.html.in > +++ b/docs/kbase.html.in > @@ -29,6 +29,9 @@ > <dt><a href="kbase/backing_chains.html">Backing chain management</a></dt> > <dd>Explanation of how disk backing chain specification impacts libvirt's > behaviour and basic troubleshooting steps of disk problems.</dd> > + > + <dt><a href="kbase/virtiofs.html">Virtio-FS</a></dt> > + <dd>Share a filesystem between the guest and the host</dd> > </dl> > </div> > > diff --git a/docs/kbase/virtiofs.rst b/docs/kbase/virtiofs.rst > new file mode 100644 > index 0000000000..e76ff8ca4b > --- /dev/null > +++ b/docs/kbase/virtiofs.rst > @@ -0,0 +1,152 @@ > +============================ > +Sharing files with Virtio-FS > +============================ > + > +=== 8< delete before merging 8< === > +NOTE: if you're looking at this note, this is just a proposal. > +See the up-to-date version on: https://libvirt.org/kbase/virtiofs.html > +=== 8< --------------------- 8< === ...this shouldn't be here still > + > +.. contents:: > + > +========= > +Virtio-FS > +========= > + > +Virtio-FS is a shared file system that lets virtual machines access > +a directory tree on the host. Unlike existing approaches, it > +is designed to offer local file system semantics and performance. > + > +See https://virtio-fs.gitlab.io/ > + > +========== > +Host setup > +========== > + > +The host-side virtiofsd daemon, like other vhost-user backed devices, > +requres shared memory between the host and the guest. As of QEMU 4.2, this requires > +requires specifying a NUMA topology for the guest and explicitly specifying > +a memory backend. Multiple options are available: > + > +Either of the following: > + > +\a) Use file-backed memory Why are you disabling list-ification here & throughout the file ? > + > +Configure the directory where the files backing the memory will be stored > +with the ``memory_backing_dir`` option in ``/etc/libvirt/qemu.conf`` > + > +:: > + > + # This directory is used for memoryBacking source if configured as file. > + # NOTE: big files will be stored here > + memory_backing_dir = "/dev/shm/" > + > +\b) Use hugepage-backed memory > + > +Make sure there are enough huge pages allocated for the requested guest memory. > +For example, for one guest with 2 GiB of RAM backed by 2 MiB hugepages: > + > +:: > + > + # virsh allocpages 2M 1024 I'm not understanding from this how big the files will be for virtiofsd ? How much memory should users expect to be needed per-guest per-virtiofsd ?