[Swan-dev] [Testing] Libreswan Testing Future - Call Notes (from May 16)

Ondrej Moris omoris at redhat.com
Wed May 25 12:25:39 UTC 2016

On 05/18/2016 03:40 PM, Ondrej Moris wrote:
> Testing with KVM
> ----------------
> KVM is now used to emulate network under test. This approach is slow
> because of various reasons (not only related to KVM): slow boot of
> guests, sanity checks (eg. checking that something is not reachable
> means waiting for timeout), transmogrification slow-down, reboots of
> guests between subsequent tests need to clean-up network stacks. KVM
> approach does not scale well, it works fine for 1-3 network nodes but
> fails badly for 100. Parallel test execution does not fit into KVM by
> the same principle. The only non-network shared directory for KVM is
> represented by 9P filesystem which is rather slow, seemingly not
> maintained anymore and missing completely in RHEL. Avoiding 9P means
> using network between host and guests (eg. NFS) which might be fragile
> and potential source of problems. Last but no least, KVM seems to losing
> drive.

I dug into 9P replacement a bit more during the last days trying to find
a way how to avoid network-related solution. I got an idea to use some
smarter filesystem with separate journals and simultaneous mounts and
tried gfs2. It is widely supported in linux distributions. I played with
it for a while and it is possible to create gfs2 filesystem in a file on
host, mount it via loopback device and add it to guests as a shared raw
storage. Guests then mount it as gfs2, whoever mounts it has its own
journal, no network is involved, but... apparently a cluster is needed
to make gfs2 work and deploying a cluster is overcomplicated, number of
nodes is very limited (<=16) and it needs network in the first place.

There are no other non-network options. We can try to replace 9P by NFS
now. I will be traveling until June 7, but one of my colleagues will be
working on that. Then we can focus on KVM performance fine-tuning of
issues Antony described earlier in this thread. And I will get back to
Docker afterwards.


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