From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 851CDC43331 for ; Thu, 26 Mar 2020 10:00:44 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 60CE62070A for ; Thu, 26 Mar 2020 10:00:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60CE62070A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jHPJI-0002xb-Kz; Thu, 26 Mar 2020 10:00:24 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jHPJI-0002xW-D7 for xen-devel@lists.xenproject.org; Thu, 26 Mar 2020 10:00:24 +0000 X-Inumbo-ID: 9b4d115a-6f48-11ea-8795-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 9b4d115a-6f48-11ea-8795-12813bfff9fa; Thu, 26 Mar 2020 10:00:23 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id BAC3DACFF; Thu, 26 Mar 2020 10:00:22 +0000 (UTC) To: Jan Beulich References: <20200326094557.13822-1-jgross@suse.com> <574ad265-7b49-6a60-fa74-655d81593049@suse.com> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <5ecfa9a2-32f1-cac5-da33-842a3e13a01f@suse.com> Date: Thu, 26 Mar 2020 11:00:22 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <574ad265-7b49-6a60-fa74-655d81593049@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Xen-devel] [PATCH] tools/libxl: make default of max event channels dependant on vcpus X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Anthony PERARD , xen-devel@lists.xenproject.org, Ian Jackson , Wei Liu Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 26.03.20 10:54, Jan Beulich wrote: > On 26.03.2020 10:45, Juergen Gross wrote: >> Today the maximum number of event channels for a guest is defaulting >> to 1023. For large guests with lots of vcpus this is not enough, as >> e.g. the Linux kernel uses 7 event channels per vcpu, limiting the >> guest to about 140 vcpus. > > I don't think any particular guest OS should "dictate" the default > here. What if another OS (or even a future version of Linux) requires > more than 8? And why would the value depend on number of vCPU-s but > not number and kind of virtual devices? It is a rough estimate. And with HVM guests being limited to 128 cpus anyway, this problem is more relevant for PV guests, limiting the available options for guest OS's. You can always specify a larger value in the guest config after all. Juergen