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[86.8.46.191]) by smtp.gmail.com with ESMTPSA id x186sm3202613wmg.41.2018.11.28.06.35.26 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 28 Nov 2018 06:35:26 -0800 (PST) Subject: Re: Any plans to increase the maximum number of virtual CPUs above 16? To: "Rodney W. Grimes" Cc: "freebsd-virtualization@freebsd.org" References: <201811272306.wARN6dKU003727@pdx.rh.CN85.dnsmgr.net> From: Simon Connah Message-ID: <023c89a6-12fa-69e4-5421-50a942488d7a@gmail.com> Date: Wed, 28 Nov 2018 14:35:27 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1 MIME-Version: 1.0 In-Reply-To: <201811272306.wARN6dKU003727@pdx.rh.CN85.dnsmgr.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: E30F076A64 X-Spamd-Result: default: False [-3.54 / 15.00]; TO_DN_EQ_ADDR_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_SOME(0.00)[]; R_SPF_ALLOW(-0.20)[+ip6:2a00:1450:4000::/36]; FREEMAIL_FROM(0.00)[gmail.com]; RCVD_COUNT_THREE(0.00)[3]; DKIM_TRACE(0.00)[gmail.com:+]; RCPT_COUNT_TWO(0.00)[2]; DMARC_POLICY_ALLOW(-0.50)[gmail.com,none]; MX_GOOD(-0.01)[cached: alt3.gmail-smtp-in.l.google.com]; NEURAL_HAM_SHORT(-0.94)[-0.943,0]; FROM_EQ_ENVFROM(0.00)[]; SUBJECT_ENDS_QUESTION(1.00)[]; RCVD_TLS_LAST(0.00)[]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:15169, ipnet:2a00:1450::/32, country:US]; MID_RHS_MATCH_FROM(0.00)[]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; R_DKIM_ALLOW(-0.20)[gmail.com]; FROM_HAS_DN(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; MIME_GOOD(-0.10)[text/plain]; PREVIOUSLY_DELIVERED(0.00)[freebsd-virtualization@freebsd.org]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCVD_IN_DNSWL_NONE(0.00)[9.2.4.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.4.6.8.4.0.5.4.1.0.0.a.2.list.dnswl.org : 127.0.5.0]; IP_SCORE(-0.59)[ipnet: 2a00:1450::/32(-1.48), asn: 15169(-1.36), country: US(-0.09)] X-Rspamd-Server: mx1.freebsd.org X-BeenThere: freebsd-virtualization@freebsd.org X-Mailman-Version: 2.1.29 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: Wed, 28 Nov 2018 14:35:29 -0000 On 27/11/2018 23:06, Rodney W. Grimes wrote: >> I was reading the bhyve man page and noticed that it said the maximum >> number of virtual CPUs is limited to 16. With AMD Epyc being out with 32 >> cores and 64 threads per CPU and being able to have 2 of them in one >> system this number seems rather low by modern standards. > > So you can run 4 x 16 vcpu VM's, probably more common than > someone trying to run 1 VM of 32 or 64 vcpu. > >> >> Are there any plans to increase this number to something like 32 virtual >> CPUs? > > There is work in process to change this from a compile time > kernel constant to a per VM value set using the undocumnted, > but present value in the cpu_topology option max_cpu. > > We do not want to just crank this value up as data structures > for each VM are sized on the MAXCPU connstant, and doubling > that to 32 would be fairly wasteful for low core count VM's. > Thank you for the reply. Ah, that makes sense. Nice to know that it is something that is being worked on. The only reason I really want to go above 16 vCPUs is that some other providers offer VPS instances with more vCPUs than that. I could quite happily live with 16 myself.