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Subject: [PATCH 0/2] Add alternative to deflate-on-oom
This series provides an alternative to deflate-on-oom, by adding a feature flag that lets the driver assume that all memory in the balloon will be made available when necessary. To allow the device to better fulfil that assumption, this series also adds an event queue for the driver to send OOM events to the device. Currently, if deflate-on-oom is not provided, then the guest driver does not know when, or even if, the memory in the balloon will ever be returned. Because of this, the Linux virtio balloon driver effectively unplugs memory in the balloon when deflate-on-oom is not provided. However, this can lead to compatibilty issues with userspace, since very few userspace programs actually handle hotplug of memory, and Linux's uAPIs aren't really even suited to potentially high frequency plugging and unplugging memory. With this alternative to deflate-on-oom, systems which cannot use deflate-on-oom can still run unmodified Linux programs in the guest. Since this series is already adding an event queue, it also adds an event the guest can use to inform the host of an allocation failure when trying to inflate the balloon. This provides an explicit signal that inflation may take a long time or fail altogether, which the device can then handle as it sees fit (e.g. abort the inflation attempt and tell the program making resource management decisions that it wasn't able to free enough memory from the guest). David Stevens (2): virtio-balloon: add an event queue virtio-balloon: add a responsive host feature conformance.tex | 2 ++ content.tex | 75 +++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 77 insertions(+) -- 2.35.0.rc0.227.g00780c9af4-goog
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