From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756031AbeDXFvD (ORCPT ); Tue, 24 Apr 2018 01:51:03 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:48066 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751469AbeDXFvC (ORCPT ); Tue, 24 Apr 2018 01:51:02 -0400 Subject: Re: [Xen-devel] [RFC 0/2] To introduce xenwatch multithreading (xen mtwatch) To: Juergen Gross References: <1523100355-27647-1-git-send-email-dongli.zhang@oracle.com> <20180423140911.bihiwfwtlneobgzd@citrix.com> <6c379249-886d-76ee-db9c-942967b23d80@oracle.com> 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 From: Dongli Zhang Message-ID: <9a91b19a-5556-f1ea-92d5-29f2baa0ccd5@oracle.com> Date: Tue, 24 Apr 2018 13:52:48 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8872 signatures=668698 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=870 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1804240059 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Dongli Zhang