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Re: [Xen-devel] 2016 Xen hackathon notes - xenstored

Please do get in touch if you have any packaging problems concerning OCaml.  
It's pretty good on modern Linux and FreeBSD though, and oxenstored works on 
most modern releases.

We've not got a set of patches that are suitable for upstreaming for the 
Xenstored/Irmin tree that we demonstrated at XenSummit, so please don't block 
waiting for that.


> On 28 Apr 2016, at 19:34, Luis R. Rodriguez <mcgrof@xxxxxxxxxx> wrote:
> At the 2016 Xen Hackathon I raised the topic of the default xenstored
> used. Here are my notes with some new additions and supported
> documentation. It would seem we're moving to oxenstored as the default
> on Linux distributions and FreeBSD now, if you have issues or concerns
> with this please let us know.
> Notes:
> =====
> Although we have had oxenstored be the the default *iff* you have
> ocaml dev libs installled when compiling Xen from source both Linux
> distributions (Debian, SUSE*, Gentoo) and FreeBSD were still using the
> C xenstored as the default. This begged the question of why not make
> the switch given Citrix has already been using oxensotred in
> production for years with these known gains [0]:
>  * 1/5th the size in terms of line of code in comparison to the C xenstored
>  * better performance increasing support for the number of guests, it
>    supports 3 times number of guests for an upper limit of 160 guests
> At the 2014 summit Anil's presented work on a Xenstore 2.0 which
> hinted also towards the future ability to provide git-like
> capabilities for the xenstore, all still written in Ocaml [1]. There
> are others who have worked on a C++ replacement lixs (Lightweight
> XenStore) as well [2], such work revealed oxenstored had the CPU
> pegged after just a few dozen guests. Such work hinted that the
> oxenstored that should be considered for more serious work was the
> Mirage OS xenstore [3], but that the C++ lixs was also performing
> better than the current oxenstored.
> Although there are questions about the future of the Xenestore we know
> oxenstored performs better than cxenstored and since we are building
> and using it by default already it begged the question why haven't
> distributions made the switch to use it by default. Since Mirage OS
> work seems promising we agreed to just set oxenstored as the default
> in distributions and in the future hope that Mirage's work or other
> contending efforts make it upstream to consider them as alternatives.
> Given Mirage Xenstore would still require ocaml, it would be a good
> stepping stone now to just use oxenstored by default more widely on
> Linux distributions and FreeBSD. A concern was raised about expertise
> over Ocaml, however it would seem that we will have no option but to
> rely on the community / folks supporting upstream oxenstored for this.
> [0] 
> http://www.do-not-panic.com/2014/04/summary-of-gains-of-xen-oxenstored.html
> [1] http://decks.openmirage.org/xendevsummit14#/
> [2] 
> http://events.linuxfoundation.org/sites/events/files/slides/xendevsummit14_0.pdf
> [3] https://github.com/mirage/ocaml-xenstore
>  Luis

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