From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59704) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XtxVa-0005SX-8L for qemu-devel@nongnu.org; Thu, 27 Nov 2014 06:45:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XtxVT-0001ql-7h for qemu-devel@nongnu.org; Thu, 27 Nov 2014 06:45:14 -0500 Received: from mailhub.sw.ru ([195.214.232.25]:38867 helo=relay.sw.ru) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XtxVS-0001ol-SR for qemu-devel@nongnu.org; Thu, 27 Nov 2014 06:45:07 -0500 From: "Denis V. Lunev" Date: Thu, 27 Nov 2014 14:45:42 +0300 Message-Id: <1417088742-4538-3-git-send-email-den@openvz.org> In-Reply-To: <1417088742-4538-1-git-send-email-den@openvz.org> References: <1417088742-4538-1-git-send-email-den@openvz.org> Subject: [Qemu-devel] [PATCH 2/2] balloon: add a feature bit to let Guest OS deflate balloon on oom List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Denis V. Lunev" , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Raushaniya Maksudova , Anthony Liguori 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. Signed-off-by: Denis V. Lunev CC: Raushaniya Maksudova CC: Anthony Liguori CC: Michael S. Tsirkin --- hw/virtio/virtio-balloon.c | 6 ++++-- include/hw/virtio/virtio-balloon.h | 2 ++ 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index 7bfbb75..4d043ce 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -305,8 +305,8 @@ static void virtio_balloon_set_config(VirtIODevice *vdev, static uint32_t virtio_balloon_get_features(VirtIODevice *vdev, uint32_t f) { - f |= (1 << VIRTIO_BALLOON_F_STATS_VQ); - return f; + VirtIOBalloon *dev = VIRTIO_BALLOON(vdev); + return (f | VIRTIO_BALLOON_F_STATS_VQ) | dev->host_features; } static void virtio_balloon_stat(void *opaque, BalloonInfo *info) @@ -409,6 +409,8 @@ static void virtio_balloon_device_unrealize(DeviceState *dev, Error **errp) } static Property virtio_balloon_properties[] = { + DEFINE_PROP_BIT("deflate-on-oom", VirtIOBalloon, host_features, + VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false), DEFINE_PROP_END_OF_LIST(), }; diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h index f863bfe..2e1ccd9 100644 --- a/include/hw/virtio/virtio-balloon.h +++ b/include/hw/virtio/virtio-balloon.h @@ -30,6 +30,7 @@ /* The feature bitmap for virtio balloon */ #define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */ #define VIRTIO_BALLOON_F_STATS_VQ 1 /* Memory stats virtqueue */ +#define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */ /* Size of a PFN in the balloon interface. */ #define VIRTIO_BALLOON_PFN_SHIFT 12 @@ -67,6 +68,7 @@ typedef struct VirtIOBalloon { QEMUTimer *stats_timer; int64_t stats_last_update; int64_t stats_poll_interval; + uint32_t host_features; } VirtIOBalloon; #endif -- 1.9.1