From nobody Wed Jul 21 12:07:33 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 24DC8127D7BE for ; Wed, 21 Jul 2021 12:07:36 +0000 (UTC) (envelope-from SRS0=OSCD=MN=quip.cz=000.fbsd@elsa.codelab.cz) Received: from elsa.codelab.cz (elsa.codelab.cz [94.124.105.4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4GVDqC6wJMz3s2G; Wed, 21 Jul 2021 12:07:35 +0000 (UTC) (envelope-from SRS0=OSCD=MN=quip.cz=000.fbsd@elsa.codelab.cz) Received: from elsa.codelab.cz (localhost [127.0.0.1]) by elsa.codelab.cz (Postfix) with ESMTP id 99AB428416; Wed, 21 Jul 2021 14:07:34 +0200 (CEST) Received: from illbsd.quip.test (ip-94-113-69-69.net.upcbroadband.cz [94.113.69.69]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by elsa.codelab.cz (Postfix) with ESMTPSA id CF1CD28417; Wed, 21 Jul 2021 14:07:33 +0200 (CEST) Subject: Re: CPU hot-plug and RAM hot-add in virtual machines To: Andriy Gapon , FreeBSD Stable Mailing List References: <4336a1bf-d826-dba3-9ec1-9b48cf7cd177@quip.cz> <70033628-bc3a-24d2-4c65-9a3b9c1c66d5@FreeBSD.org> <14d647fe-5bc3-b69e-e074-6202b2418d22@FreeBSD.org> From: Miroslav Lachman <000.fbsd@quip.cz> Message-ID: Date: Wed, 21 Jul 2021 14:07:33 +0200 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 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: <14d647fe-5bc3-b69e-e074-6202b2418d22@FreeBSD.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 4GVDqC6wJMz3s2G X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] X-ThisMailContainsUnwantedMimeParts: N On 21/07/2021 12:45, Andriy Gapon wrote: > On 21/07/2021 11:53, Miroslav Lachman wrote: >> On 09/07/2021 13:16, Andriy Gapon wrote: [..] >> 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. Thank you again. It really seems too complicated. Miroslav Lachman