From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: Users of ballooning, please come forth! Date: Fri, 21 Feb 2014 11:58:09 +1030 Message-ID: <87txbt8dau.fsf@rustcorp.com.au> References: <20140219144914.GA18487@redhat.com> <87bny2befb.fsf@rustcorp.com.au> <20140220131706.GB18487@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTP id 2916582D for ; Fri, 21 Feb 2014 02:31:01 +0000 (UTC) Received: from ozlabs.org (ozlabs.org [203.10.76.45]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id B4EF11FFF6 for ; Fri, 21 Feb 2014 02:31:00 +0000 (UTC) In-Reply-To: <20140220131706.GB18487@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Adam Litke Cc: msivak@redhat.com, Daniel Kiper , virtualization@lists.linuxfoundation.org, dfediuck@redhat.com, Luiz Capitulino List-Id: virtualization@lists.linuxfoundation.org Adam Litke writes: > On 20/02/14 14:53 +1030, Rusty Russell wrote: >>I think we're headed to the same destination here; the variant which I >>came up with (and suggested to Daniel and Luiz, CC'd) is similar: the >>guest self-balloons, giving up pages when it can, but the host sets a >>ceiling. >> >>This way, if the host really needs to set a limit, it can: a disobedient >>guest will start paging. But generally, a guest should use its >>judgement to balloon its own pages as it can (below the ceiling). > > It sounds similar but it sounds like you are suggesting one limit > value and I am suggesting two. Your ceiling value sounds like a soft > limit on total guest memory (aka minimum balloon size). This is the > more important limit of the two I have suggested. Do you think it's > also worthwhile to have a maximum balloon size (floor value) to keep > the allowable balloon size between two points? It's a little simpler to have a ceiling only. And if everyone (guests and host) are feeling like they have plenty of memory, it's probably best sitting in the host. 1) It can quickly go to a guest if necessary. 2) The host could coalesce/shuffle memory. 3) The host could turn off RAM to save power. Cheers, Rusty.