Re: [Xen-devel] [PATCH v1 09/10] libxl: introduce libxl_retrieve_domain_configuration

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Jul 17, 2014 at 11:59:01AM +0100, Ian Campbell wrote:
> On Thu, 2014-07-10 at 15:32 +0100, Wei Liu wrote:
> > Introduce a new public API to return domain configuration. This returned
> > configuration can be used to rebuild a domain.
> > 
> > Note that this configuration doesn't equal to the current state of the
> > domain. What it does is to use JSON version configuration as template
> > and pull in relevant information from xenstore.
> 
> I think this configuration does equal the current state, doesn't it?
> Isn't that the whole point?
> 

Hrm... by "current state" I mean the current running state. But to
rebuild a domain we might leave some configurations for the remote host
toolstack to decide. The configuration this API returns is (template
configuration + current state that we care about).

> > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> > index 49d7ef6..cd5914c 100644
> > --- a/tools/libxl/libxl.c
> > +++ b/tools/libxl/libxl.c
> > @@ -6034,6 +6034,206 @@ void libxl_mac_copy(libxl_ctx *ctx, libxl_mac *dst, 
> > libxl_mac *src)
> >      for (i = 0; i < 6; i++)
> >          (*dst)[i] = (*src)[i];
> >  }
> > +
> > +int libxl_retrieve_domain_configuration(libxl_ctx *ctx, uint32_t domid,
> > +                                        libxl_domain_config *d_config)
> 
> It occurs to me to wonder if any function which takes a lock ought to be
> async capable?
> 

Good point.

> Also is there is any possibility that any of the operations needed to
> gather the updated configuration might take a long time.
> 

I think reading from xenstore and filesystem can be slow, in the sense
that if there's much contention on these two resources it could take
seconds to finish operations.

> > +    /* Memory limits:
> > +     *
> > +     * Currently there're three memory limits:
> > +     *  1. "target" in xenstore (originally memory= in config file)
> > +     *  2. "static-max" in xenstore (originally maxmem= in config file)
> 
> Nit: strictly speaking those "originally..." are xl specific and this is
> libxl. </pendant>
> 

You mean I should write "originally memory= in xl config file"?

Wei.

> Ian.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel