From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57692) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y0SVp-00028s-51 for qemu-devel@nongnu.org; Mon, 15 Dec 2014 05:04:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y0SVj-0003s9-Kq for qemu-devel@nongnu.org; Mon, 15 Dec 2014 05:04:21 -0500 Received: from relay.parallels.com ([195.214.232.42]:35315) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y0SVj-0003s4-Cn for qemu-devel@nongnu.org; Mon, 15 Dec 2014 05:04:15 -0500 Message-ID: <548EB20E.80509@openvz.org> Date: Mon, 15 Dec 2014 13:03:58 +0300 From: "Denis V. Lunev" MIME-Version: 1.0 References: <1417092255-4672-1-git-send-email-den@openvz.org> In-Reply-To: <1417092255-4672-1-git-send-email-den@openvz.org> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3 0/2] balloon: add a feature bit to let Guest OS deflate virtio_balloon on OOM List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Michael S. Tsirkin" , qemu-devel@nongnu.org, Raushaniya Maksudova , Anthony Liguori On 27/11/14 15:44, Denis V. Lunev wrote: > Excessive virtio_balloon inflation can cause invocation of OOM-killer, > when Linux is under severe memory pressure. Various mechanisms are > responsible for correct virtio_balloon memory management. Nevertheless it > is often the case that these control tools does not have enough time to > react on fast changing memory load. As a result OS runs out of memory and > invokes OOM-killer. The balancing of memory by use of the virtio balloon > should not cause the termination of processes while there are pages in the > balloon. Now there is no way for virtio balloon driver to free memory at > the last moment before some process get killed by OOM-killer. > > This does not provide a security breach as balloon itself is running > inside Guest OS and is working in the cooperation with the host. Thus > some improvements from Guest side should be considered as normal. > > To solve the problem, introduce a virtio_balloon callback which is > expected to be called from the oom notifier call chain in out_of_memory() > function. If virtio balloon could release some memory, it will make the > system to return and retry the allocation that forced the out of memory > killer to run. > > This behavior should be enabled if and only if appropriate feature bit > is set on the device. It is off by default. > > This functionality was recently merged into vanilla Linux (actually in > linux-next at the moment) > > commit 5a10b7dbf904bfe01bb9fcc6298f7df09eed77d5 > Author: Raushaniya Maksudova > Date: Mon Nov 10 09:36:29 2014 +1030 > > This patch adds respective control bits into QEMU. It introduces > deflate-on-oom option for baloon device which do the trick. > > Changes from v2: > - fixed mistake with bit number in virtio_balloon_get_features > > Changes from v1: > - From: in patch 1 according to the original ownership > - feature processing in patch 2 as suggested by Michael. It could be done > without additional field, but this will require to move the property > level up, i.e. to PCI & CCW level. > > Signed-off-by: Raushaniya Maksudova > Signed-off-by: Denis V. Lunev > CC: Anthony Liguori > CC: Michael S. Tsirkin > ping