Re: [Xen-devel] Re: Next steps with pv_ops for Xen

[tgh <wwwwww4187@xxxxxxxxxxx>]

hi
I am not quite clear about the purpose of pv-ops , what do we want to 
deal with by developping "pv-ops"? is it used for HVM or for PV or KVM 
or something ? I have seen it for a few months in the list ,and 
"pv-ops"is an active project ,but i am not clear about what is the aim 
of "pv-ops" ,could you give me an explanation about it
Thanks in advance




Mark Williamson åé:
> > Hi Mark,
> >
> >     
> > > Maybe a change to the gntdev userspace API to allow batching
> > > of mapping requests?
> > >       
> > Something along the lines of the following?
> >     
> Just like that :-D
>
> When you said "multiple syscalls per mapping" I assumed you meant that we'd 
> lose the batching you get by doing a mulicall.  If it's just a couple of 
> syscalls (plus, presumably a couple of hypercalls) per batch of mappings, my 
> gut says it's probably not going to hurt block performance.  My guts have 
> been wrong in (many!) ways before of course...
> I guess the overhead *could* be reduced even more by just having a magic ioctl 
> that did all the mmap-ing stuff in one operation, but that'd probably be 
> really gross if it wasn't necessary!  And I doubt it'd make upstream very 
> happy...
> We'll also be eliminating the overheads involved in having a blktap ring for 
> talking to userspace and having to move requests between that ring and the 
> real block ring, so there's some definite wins in overheads as well.
> Cheers,
> Mark
>
>   

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