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

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.


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