From owner-freebsd-virtualization@freebsd.org Tue Feb 13 23:49:05 2018 Return-Path: Delivered-To: freebsd-virtualization@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 59CC2F0C67E for ; Tue, 13 Feb 2018 23:49:05 +0000 (UTC) (envelope-from grehan@freebsd.org) Received: from alto.onthenet.com.au (alto.OntheNet.com.au [203.13.68.12]) by mx1.freebsd.org (Postfix) with ESMTP id BB6D678EAF for ; Tue, 13 Feb 2018 23:49:04 +0000 (UTC) (envelope-from grehan@freebsd.org) Received: from iredmail.onthenet.com.au (iredmail.onthenet.com.au [203.13.68.150]) by alto.onthenet.com.au (Postfix) with ESMTPS id CFF1620B4D34 for ; Wed, 14 Feb 2018 09:49:01 +1000 (AEST) Received: from localhost (iredmail.onthenet.com.au [127.0.0.1]) by iredmail.onthenet.com.au (Postfix) with ESMTP id C647E281F1F for ; Wed, 14 Feb 2018 09:49:01 +1000 (AEST) X-Amavis-Modified: Mail body modified (using disclaimer) - iredmail.onthenet.com.au Received: from iredmail.onthenet.com.au ([127.0.0.1]) by localhost (iredmail.onthenet.com.au [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id sRzo1bk7CNro for ; Wed, 14 Feb 2018 09:49:01 +1000 (AEST) Received: from Peters-MacBook-Pro-2.local (96-82-80-65-static.hfc.comcastbusiness.net [96.82.80.65]) by iredmail.onthenet.com.au (Postfix) with ESMTPSA id 2FD32280AB0; Wed, 14 Feb 2018 09:48:59 +1000 (AEST) Subject: Re: bhyve and contention To: "Rodney W. Grimes" , tech-lists Cc: freebsd-virtualization@freebsd.org References: <201802131806.w1DI6xp7049909@pdx.rh.CN85.dnsmgr.net> From: Peter Grehan Message-ID: Date: Tue, 13 Feb 2018 15:48:57 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <201802131806.w1DI6xp7049909@pdx.rh.CN85.dnsmgr.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-CMAE-Score: 0 X-CMAE-Analysis: v=2.3 cv=KPZ08mNo c=1 sm=1 tr=0 a=A6CF0fG5TOl4vs6YHvqXgw==:117 a=mwgbnDbW7alINpy3vhoKyg==:17 a=IkcTkHD0fZMA:10 a=Op4juWPpsa0A:10 a=RbfNA_8WEnTZXyLG25AA:9 a=QEXdDO2ut3YA:10 wl=host:3 X-BeenThere: freebsd-virtualization@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: "Discussion of various virtualization techniques FreeBSD supports." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 13 Feb 2018 23:49:05 -0000 >> 2. >> In the following context, the server is the same but this time all five >> guests have -c 4 per guest, so bhyve is asking 12 more cores than that >> existing in hardware. Does the guest fail to load, do either guest or >> server crash? > > The is core over commit, very common in the virtualization world, > bhyve does its best effort to give the guests cores as needed. To add to what Rod said - bhyve uses a thread for each vCPU. It's up to the FreeBSD scheduler to determine where/when these threads run. It is possible for a guest to fail, for example if a spinlock times out due to vCPUs not being able to run to release a lock. This is a general problem with virtualization and can occur even on VMWare ESXi with heavy oversubscription. That being said, there is certainly scope to provide more information to the FreeBSD scheduler so it can make better decisions when running VM guests. later, Peter.