bhyve uses all available memory during IO-intensive operations

[Dustin Wenz]

I'm using chyves on FreeBSD 11.1 RELEASE to manage a few VMs (guest OS is also FreeBSD 11.1). Their sole purpose is to house some medium-sized Postgres databases (100-200GB). The host system has 64GB of real memory and 112GB of swap. I have configured each guest to only use 16GB of memory, yet while doing my initial database imports in the VMs, bhyve will quickly grow to use all available system memory and then be killed by the kernel:

	kernel: swap_pager: I/O error - pageout failed; blkno 1735,size 4096, error 12
	kernel: swap_pager: I/O error - pageout failed; blkno 1610,size 4096, error 12
	kernel: swap_pager: I/O error - pageout failed; blkno 1763,size 4096, error 12
	kernel: pid 41123 (bhyve), uid 0, was killed: out of swap space

The OOM condition seems related to doing moderate IO within the VM, though nothing within the VM itself shows high memory usage. This is the chyves config for one of them:

	bargs                      -A -H -P -S
	bhyve_disk_type            virtio-blk
	bhyve_net_type             virtio-net
	bhyveload_flags
	chyves_guest_version       0300
	cpu                        4
	creation                   Created on Mon Oct 23 16:17:04 CDT 2017 by chyves v0.2.0 2016/09/11 using __create()
	loader                     bhyveload
	net_ifaces                 tap51
	os                         default
	ram                        16G
	rcboot                     0
	revert_to_snapshot
	revert_to_snapshot_method  off
	serial                     nmdm51
	template                   no
	uuid                       8495a130-b837-11e7-b092-0025909a8b56


I've also tried using different bhyve_disk_types, with no improvement. How is it that bhyve can use far more memory that I'm specifying?

	- .Dustin
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