Re: [Xen-devel] xc_domain_getinfolist() declaration

[Daniel Veillard <veillard@xxxxxxxxxx>]

On Mon, Oct 24, 2005 at 02:27:52PM -0500, Anthony Liguori wrote:
> Daniel Veillard wrote:
> 
> >I would expect xc_domain_getinfolist() to just be an extended version
> >of xc_domain_getinfo() but filling-up a range of xc_dominfo_t. However
> >the declaration in xenctrl.h is 
> >
> > int xc_domain_getinfolist(int xc_handle,
> >                           uint32_t first_domain,
> >                         unsigned int max_domains,
> >                         xc_domaininfo_t *info);
> >
> >i.e. a different info pointer type than
> >
> > int xc_domain_getinfo(int xc_handle,
> >                       uint32_t first_domid,
> >                     unsigned int max_doms,
> >                     xc_dominfo_t *info);
> >
> >is that a typo ? xc_domaininfo_t is defined as dom0_getdomaininfo_t
> >which is a distinct type from xc_dominfo_t, with slightly different 
> >characteristics. Any reason for that disparity in the type returned
> >between those two functions ?
> > 
> >
> xc_domain_getinfolist is a batched interface to xc_domain_getinfo from 
> the hypervisor perspective.  That is, getinfolist will only make a 
> single hypercall whereas getinfo will make up to max_doms hypercalls.
> 
> getinfo massages the returned data into a more python friendly structure 
> (xc_dominfo_t) whereas getinfolist returns the raw results from the 
> hypercall (which is just typedef'd to xc_domaininfo_t.
> 
> The argument for getinfolist was performance.  Applications that require 
> as low-overhead as possible polling info polling mechanism can use 
> getinfolist.

  Okay, thanks !

Daniel

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Daniel Veillard      | Red Hat http://redhat.com/
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