e3816255bf
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 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. commit 5a10b7dbf904bfe01bb9fcc6298f7df09eed77d5 Author: Raushaniya Maksudova <rmaksudova@parallels.com> Date: Mon Nov 10 09:36:29 2014 +1030 This patch adds respective control bits into QEMU. It introduces deflate-on-oom option for balloon device which does the trick. Signed-off-by: Denis V. Lunev <den@openvz.org> CC: Raushaniya Maksudova <rmaksudova@parallels.com> CC: Anthony Liguori <aliguori@amazon.com> CC: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: James Bottomley <JBottomley@Odin.com> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
49 lines
1.2 KiB
C
49 lines
1.2 KiB
C
/*
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* Virtio Support
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*
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* Copyright IBM, Corp. 2007-2008
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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* Rusty Russell <rusty@rustcorp.com.au>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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#ifndef _QEMU_VIRTIO_BALLOON_H
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#define _QEMU_VIRTIO_BALLOON_H
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#include "standard-headers/linux/virtio_balloon.h"
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#include "hw/virtio/virtio.h"
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#include "hw/pci/pci.h"
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#define TYPE_VIRTIO_BALLOON "virtio-balloon-device"
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#define VIRTIO_BALLOON(obj) \
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OBJECT_CHECK(VirtIOBalloon, (obj), TYPE_VIRTIO_BALLOON)
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typedef struct virtio_balloon_stat VirtIOBalloonStat;
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typedef struct virtio_balloon_stat_modern {
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uint16_t tag;
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uint8_t reserved[6];
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uint64_t val;
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} VirtIOBalloonStatModern;
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typedef struct VirtIOBalloon {
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VirtIODevice parent_obj;
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VirtQueue *ivq, *dvq, *svq;
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uint32_t num_pages;
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uint32_t actual;
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uint64_t stats[VIRTIO_BALLOON_S_NR];
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VirtQueueElement stats_vq_elem;
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size_t stats_vq_offset;
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QEMUTimer *stats_timer;
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int64_t stats_last_update;
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int64_t stats_poll_interval;
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uint32_t host_features;
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} VirtIOBalloon;
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#endif
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