Projects/auto-ballooning

LuizCapitulino — Mon, 17 Jun 2013 21:09:58 GMT

Revision as of 21:09, 17 June 2013		Current revision
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	When a Linux host is running out of memory, the kernel will take action to ''reclaim'' memory. This action may be detrimental to KVM guests performace (eg. swapping) or even extreme to the point where the kernel may kill a VM or an important virt stack component.		When a Linux host is running out of memory, the kernel will take action to ''reclaim'' memory. This action may be detrimental to KVM guests performace (eg. swapping) or even extreme to the point where the kernel may kill a VM or an important virt stack component.

-	To help avoiding this situation, a KVM guest could automatically return memory to the host when the host is facing memory pressure (automatic inflate). By doing so the guest may also get into memory pressure so we also need a way to allow the guest to automatically get memory back (automatic deflate).	+	To help avoiding this situation, a KVM guest could automatically return memory to the host when the host is facing memory pressure. By doing so the guest may also get into memory pressure so we also need a way to allow the guest to automatically get memory back.

	That's what the automatic ballooning project is about. The next section will dive into ways of implementing it. The following section will provide instructions on how to try current patches.		That's what the automatic ballooning project is about. The next section will dive into ways of implementing it. The following section will provide instructions on how to try current patches.
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	=== Automatic Deflate ===		=== Automatic Deflate ===

-	Automatic deflate is performed by the virtio-balloon driver in the guest. There's also two ways of implementing this:	+	Automatic deflate is performed by the virtio-balloon driver within the guest. There's also two ways of implementing this:

	# The virtio-balloon driver registers a callback with the shrinker API. That callback is called when the guest kernel is facing memory pressure. The number of pages to be returned to the kernel is passed to the callback, so that the callback can deflate the balloon by that amount. This is what the current patchset does		# The virtio-balloon driver registers a callback with the shrinker API. That callback is called when the guest kernel is facing memory pressure. The number of pages to be returned to the kernel is passed to the callback, so that the callback can deflate the balloon by that amount. This is what the current patchset does
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	== Testing ==		== Testing ==
		+
		+	You have to do three things to play with automatic-ballooning:
		+
		+	# Install kernel 3.10-rc1 or higher in the host. Make sure to enable CONFIG_CGROUPS and CONFIG_MEMCG
		+	# Clone QEMU from ''git://repo.or.cz/qemu/qmp-unstable.git balloon/auto-ballooning/rfc.v2'' (or grab the patch [http://repo.or.cz/w/qemu/qmp-unstable.git/commit/59fec94e6396d6c32cdce47777440c3a988be63d here])
		+	# Install the following kernel on your guest ''git://repo.or.cz/linux-2.6/luiz-linux-2.6.git virtio-balloon/auto-deflate/rfc'' (or grab the patches from the [http://repo.or.cz/w/linux-2.6/luiz-linux-2.6.git/shortlog/refs/heads/virtio-balloon/auto-deflate/rfc web interface])
		+
		+	After setting up the above, do the following to experiment with automatic deflate (which is easy to reproduce):
		+
		+	# Pass ''-balloon virtio,auto-balloon=true'' when starting QEMU
		+	# Wait for the guest to boot, then generate some memory pressure in the guest (say a kernel build with lots of jobs)
		+	# Switch to QEMU's monitor and decrease guest memory (say from 1G to 200MB)
		+	# Watch the guest increase its memory by repeatedly running "info balloon" on QEMU's monitor
		+
		+	To see automatic inflate and automatic deflate in action, you can run several VMs in parallel doing some heavy memory workload. Make sure to over commit host memory. Say your host has 4GB, run 6 VMs with 1GB each.
		+
		+	Another idea is to run one VM, but generate pressure in the host some way like a big kernel build or an application that allocates lots of memory.

OVMF

Lersek — Sat, 15 Jun 2013 13:42:26 GMT

update win2k8r2sp1 guest status

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Projects/auto-ballooning

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