On Thu, Nov 27, 2014 at 03:50:11PM +0400, Andrey Korolyov wrote: > On Thu, Nov 27, 2014 at 2:45 PM, Denis V. Lunev <d...@openvz.org> 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 <rmaksud...@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 baloon device which do the trick. > > > > Signed-off-by: Denis V. Lunev <d...@openvz.org> > > CC: Raushaniya Maksudova <rmaksud...@parallels.com> > > CC: Anthony Liguori <aligu...@amazon.com> > > CC: Michael S. Tsirkin <m...@redhat.com>
... > Had you tried this with a system-wide OOM on a real workload? This > behavior can work perfectly with dedicated memory cgroups, but I`m > afraid it would be unusable when entire system stalls and waits for a > balloon deflation. That's really a question about guest drivers though, isn't it? So you aren't responding to correct patches, and aren't copying the correct people. -- MST
