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[209.132.183.28]) by mx.google.com with ESMTPS id n10si2958397uao.24.2019.07.18.13.37.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Jul 2019 13:37:58 -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-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E683881F0C; Thu, 18 Jul 2019 20:37:57 +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 7D93B1001B35; Thu, 18 Jul 2019 20:37:45 +0000 (UTC) Date: Thu, 18 Jul 2019 16:37:44 -0400 From: "Michael S. Tsirkin" To: Alexander Duyck Cc: Nitesh Narayan Lal , 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: <20190718163325-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> <20190718113548-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 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Thu, 18 Jul 2019 20:37:58 +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 01:29:14PM -0700, Alexander Duyck wrote: > So one thing that is still an issue then is that my approach would > only work on the first migration. The problem is the logic I have > implemented assumes that once we have hinted on a page we don't need > to do it again. However in order to support migration you would need > to reset the hinting entirely and start over again after doing a > migration. Well with precopy at least it's simple: just clear the dirty bit, it won't be sent, and then on destination you get a zero page and later COW on first write. Right? With precopy it is tricker as destination waits until it gets all of memory. I think we could use some trick to make source pretend it's a zero page, that is cheap to send. -- MST