From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756205AbeDXGDY (ORCPT ); Tue, 24 Apr 2018 02:03:24 -0400 Received: from mx2.suse.de ([195.135.220.15]:45349 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755919AbeDXGDV (ORCPT ); Tue, 24 Apr 2018 02:03:21 -0400 Subject: Re: [Xen-devel] [RFC 0/2] To introduce xenwatch multithreading (xen mtwatch) To: Dongli Zhang Cc: Wei Liu , ian.jackson@eu.citrix.com, linux-kernel@vger.kernel.org, srinivas.eeda@oracle.com, xen-devel@lists.xenproject.org, boris.ostrovsky@oracle.com, Joao Martins References: <1523100355-27647-1-git-send-email-dongli.zhang@oracle.com> <20180423140911.bihiwfwtlneobgzd@citrix.com> <6c379249-886d-76ee-db9c-942967b23d80@oracle.com> <9a91b19a-5556-f1ea-92d5-29f2baa0ccd5@oracle.com> From: Juergen Gross Message-ID: <0280ae73-fd29-33a6-e4d5-8c83a8c2a5d7@suse.com> Date: Tue, 24 Apr 2018 08:03:18 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <9a91b19a-5556-f1ea-92d5-29f2baa0ccd5@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: de-DE Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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/'. >>>>> >>>>> 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. Juergen