Re: [Xen-devel] xc_domain_getinfolist() declaration

[Anthony Liguori <aliguori@xxxxxxxxxx>]

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.
Regards,

Anthony Liguori

> Daniel
>
>  

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