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Date: Tue, 24 Apr 2018 13:52:48 +0800 From: Dongli Zhang <dongli.zhang@...cle.com> To: Juergen Gross <jgross@...e.com> Cc: Wei Liu <wei.liu2@...rix.com>, ian.jackson@...citrix.com, linux-kernel@...r.kernel.org, srinivas.eeda@...cle.com, xen-devel@...ts.xenproject.org, boris.ostrovsky@...cle.com, Joao Martins <joao.m.martins@...cle.com> Subject: Re: [Xen-devel] [RFC 0/2] To introduce xenwatch multithreading (xen mtwatch) 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. Dongli Zhang
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