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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 some memory at the last moment before some process will be 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. Allocate virtio feature bit for this: it is not set by default, the the guest will not deflate virtio balloon on OOM without explicit permission from host. Signed-off-by: Raushaniya Maksudova <rmaksudova@parallels.com> Signed-off-by: Denis V. Lunev <den@openvz.org> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
61 lines
2.7 KiB
C
61 lines
2.7 KiB
C
#ifndef _LINUX_VIRTIO_BALLOON_H
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#define _LINUX_VIRTIO_BALLOON_H
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/* This header is BSD licensed so anyone can use the definitions to implement
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* compatible drivers/servers.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of IBM nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE. */
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#include <linux/virtio_ids.h>
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#include <linux/virtio_config.h>
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/* The feature bitmap for virtio balloon */
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#define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */
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#define VIRTIO_BALLOON_F_STATS_VQ 1 /* Memory Stats virtqueue */
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#define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */
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/* Size of a PFN in the balloon interface. */
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#define VIRTIO_BALLOON_PFN_SHIFT 12
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struct virtio_balloon_config
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{
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/* Number of pages host wants Guest to give up. */
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__le32 num_pages;
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/* Number of pages we've actually got in balloon. */
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__le32 actual;
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};
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#define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */
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#define VIRTIO_BALLOON_S_SWAP_OUT 1 /* Amount of memory swapped out */
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#define VIRTIO_BALLOON_S_MAJFLT 2 /* Number of major faults */
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#define VIRTIO_BALLOON_S_MINFLT 3 /* Number of minor faults */
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#define VIRTIO_BALLOON_S_MEMFREE 4 /* Total amount of free memory */
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#define VIRTIO_BALLOON_S_MEMTOT 5 /* Total amount of memory */
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#define VIRTIO_BALLOON_S_NR 6
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struct virtio_balloon_stat {
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__u16 tag;
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__u64 val;
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} __attribute__((packed));
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#endif /* _LINUX_VIRTIO_BALLOON_H */
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