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[209.132.183.28]) by mx.google.com with ESMTPS id a25si4904717uaq.15.2019.07.18.13.28.14 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Jul 2019 13:28:14 -0700 (PDT) Received-SPF: pass (google.com: domain of mst@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of mst@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=mst@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com 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) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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