Messages in this thread | | | Subject | Re: [Xen-devel] [RFC 0/2] To introduce xenwatch multithreading (xen mtwatch) | From | Dongli Zhang <> | Date | Tue, 24 Apr 2018 14:10:40 +0800 |
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On 04/24/2018 02:03 PM, Juergen Gross wrote: > On 24/04/18 07:52, Dongli Zhang wrote: >> Hi Juergen, >> >> On 04/24/2018 01:22 PM, Juergen Gross wrote: >>> On 24/04/18 01:55, Dongli Zhang wrote: >>>> Hi Wei, >>>> >>>> On 04/23/2018 10:09 PM, Wei Liu wrote: >>>>> On Sat, Apr 07, 2018 at 07:25:53PM +0800, Dongli Zhang wrote: >>>>>> About per-domU xenwatch thread create/destroy, a new type of xenstore node is >>>>>> introduced: '/local/domain/0/mtwatch/<domid>'. >>>>>> >>>>>> Suppose the new domid id 7. During the domU (domid=7) creation, the xen >>>>>> toolstack writes '/local/domain/0/mtwatch/7' to xenstore before the insertion >>>>>> of '/local/domain/7'. When the domid=7 is destroyed, the last xenstore >>>>>> operation by xen toolstack is to remove '/local/domain/0/mtwatch/7'. >>>>>> >>>>>> The dom0 kernel subscribes a watch at node '/local/domain/0/mtwatch'. Kernel >>>>>> thread [xen-mtwatch-7] is created when '/local/domain/0/mtwatch/7' is inserted, >>>>>> while this kernel thread is destroyed when the corresponding xenstore node is >>>>>> removed. >>>>> >>>>> Instead of inventing yet another node, can you not watch /local/domain >>>>> directly? >>>> >>>> Would you like to watch at /local/domain directly? Or is your question "is there >>>> any other way to not watch at /local/domain, while no extra xenstore node will >>>> be introduced"? >>>> >>>> Actually, the first prototype of this idea was to watch at /local/domain >>>> directly to get aware of the domU create/destroy, so that xen toolstack will not >>>> get involved. Joao Martins (CCed) had a concern on the performance as watching >>>> at /local/domain would lead to large amount of xenwatch events. >>> >>> That's what the special watches "@introduceDomain" and "@releaseDomain" >>> are meant for. >> >> I used to consider to watch at "@introduceDomain". However, there is no domain >> information appended with "@introduceDomain" and it is still required for dom0 >> kernel to proactively confirm who is created. > > That isn't too hard, right? You just need to read /local/domain to get > the list of its children and look for new domains there.
You are right. I will try to limit the modification within linux kernel, and try to not dirty xen toolstack.
Thank you very much for the suggestion.
Dongli Zhang
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