From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50487) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y2zMW-00023f-Qc for qemu-devel@nongnu.org; Mon, 22 Dec 2014 04:33:17 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y2zMS-0002Vv-Cf for qemu-devel@nongnu.org; Mon, 22 Dec 2014 04:33:12 -0500 Received: from relay.parallels.com ([195.214.232.42]:41945) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y2zMS-0002KO-6M for qemu-devel@nongnu.org; Mon, 22 Dec 2014 04:33:08 -0500 Message-ID: <5497E01B.8000108@parallels.com> Date: Mon, 22 Dec 2014 12:10:51 +0300 From: "Denis V. Lunev" MIME-Version: 1.0 References: <1417092255-4672-1-git-send-email-den@openvz.org> <548EB20E.80509@openvz.org> In-Reply-To: <548EB20E.80509@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 15/12/14 13:03, Denis V. Lunev wrote: > 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 ping. Corresponding changes have been just merged into vanilla Linux.