From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7D64BC76195 for ; Thu, 18 Jul 2019 20:28:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F982204FD for ; Thu, 18 Jul 2019 20:28:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391376AbfGRU2O (ORCPT ); Thu, 18 Jul 2019 16:28:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58122 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727687AbfGRU2O (ORCPT ); Thu, 18 Jul 2019 16:28:14 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B13D4C060201; Thu, 18 Jul 2019 20:28:13 +0000 (UTC) Received: from redhat.com (ovpn-120-147.rdu2.redhat.com [10.10.120.147]) by smtp.corp.redhat.com (Postfix) with SMTP id 9E80D5D71C; Thu, 18 Jul 2019 20:27:56 +0000 (UTC) Date: Thu, 18 Jul 2019 16:27:55 -0400 From: "Michael S. Tsirkin" To: Nitesh Narayan Lal Cc: Alexander Duyck , kvm list , David Hildenbrand , Dave Hansen , LKML , linux-mm , Andrew Morton , Yang Zhang , pagupta@redhat.com, Rik van Riel , Konrad Rzeszutek Wilk , lcapitulino@redhat.com, wei.w.wang@intel.com, Andrea Arcangeli , Paolo Bonzini , dan.j.williams@intel.com, Alexander Duyck Subject: Re: [PATCH v1 6/6] virtio-balloon: Add support for aerating memory via hinting Message-ID: <20190718162502-mutt-send-email-mst@kernel.org> References: <20190716115535-mutt-send-email-mst@kernel.org> <20190716125845-mutt-send-email-mst@kernel.org> <20190717055804-mutt-send-email-mst@kernel.org> <20190718003211-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 18 Jul 2019 20:28:13 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Jul 18, 2019 at 12:03:23PM -0400, Nitesh Narayan Lal wrote: > >>>> For example we allocate pages until shrinker kicks in. > >>>> Fair enough but in fact many it would be better to > >>>> do the reverse: trigger shrinker and then send as many > >>>> free pages as we can to host. > >>> I'm not sure I understand this last part. > >> Oh basically what I am saying is this: one of the reasons to use page > >> hinting is when host is short on memory. In that case, why don't we use > >> shrinker to ask kernel drivers to free up memory? Any memory freed could > >> then be reported to host. > > Didn't the balloon driver already have a feature like that where it > > could start shrinking memory if the host was under memory pressure? > If you are referring to auto-ballooning (I don't think it is merged). It > has its own set of disadvantages such as it could easily lead to OOM, > memory corruption and so on. Right. So what I am saying is: we could have a flag that triggers a shrinker once before sending memory hints. Worth considering. -- MST