From nobody Wed Jul 21 10:45:52 2021 X-Original-To: freebsd-stable@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id B3D7012B4564 for ; Wed, 21 Jul 2021 10:45:55 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from smtp.freebsd.org (smtp.freebsd.org [96.47.72.83]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "smtp.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4GVC0z4pk3z3LZB; Wed, 21 Jul 2021 10:45:55 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from [192.168.0.88] (unknown [195.64.148.76]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) (Authenticated sender: avg/mail) by smtp.freebsd.org (Postfix) with ESMTPSA id 36CD12709C; Wed, 21 Jul 2021 10:45:55 +0000 (UTC) (envelope-from avg@FreeBSD.org) From: Andriy Gapon To: Miroslav Lachman <000.fbsd@quip.cz>, FreeBSD Stable Mailing List References: <4336a1bf-d826-dba3-9ec1-9b48cf7cd177@quip.cz> <70033628-bc3a-24d2-4c65-9a3b9c1c66d5@FreeBSD.org> Subject: Re: CPU hot-plug and RAM hot-add in virtual machines Message-ID: <14d647fe-5bc3-b69e-e074-6202b2418d22@FreeBSD.org> Date: Wed, 21 Jul 2021 13:45:52 +0300 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.12.0 List-Id: Production branch of FreeBSD source code List-Archive: https://lists.freebsd.org/archives/freebsd-stable List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-stable@freebsd.org X-BeenThere: freebsd-stable@freebsd.org MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-ThisMailContainsUnwantedMimeParts: N On 21/07/2021 11:53, Miroslav Lachman wrote: > On 09/07/2021 13:16, Andriy Gapon wrote: >> On 08/07/2021 00:34, Miroslav Lachman wrote: >>> The question is simple but I cannot find answer - Does FreeBSD support >>> hot-plug vCPU and hot-add RAM? >>> Current virtualization platforms support adding CPU cores or additional RAM >>> without the need to reboot the guest OS. Some of our clients need to add >>> additional vCPUs or RAM so often that hot-plug and hot-add will be really >>> useful. If this is not supported on FreeBSD for now, is there any Work In >>> Progress? Or is there a plan to support it? >> >> I think that those features are not supported and I haven't heard of any WIP. > > Thank you for your reply. I know nothing about system internals. Is it too much > work to implement it or just nobody from developers need it thus nobody write > the code? Virtualization is more and more popular these days so I think it will > be useful for many users. In my opinion, both would be big changes. At the moment we do not have any support for offlining / onlining CPUs and that would involve a lot of careful changes like safely updating CPU sets, various CPU masks, etc. Ditto for the memory. Updating page arrays, free memory accounting structures, possibly some memory maps, etc. Definitely not a weekend project. -- Andriy Gapon