bhyve uses all available memory during IO-intensive operations

[Dustin Wenz]

I am using a zvol as the storage for the VM, and I do not have any ARC limits set. However, the bhyve process itself ends up grabbing the vast majority of memory. 

I’ll run a test tomorrow to get the exact output from top.

   - .Dustin

> On Nov 30, 2017, at 5:28 PM, Allan Jude <allanjude at freebsd.org> wrote:
> 
>> On 11/30/2017 18:15, Dustin Wenz wrote:
>> 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
>> 
> 
> Can you show 'top' output. What makes you think bhyve is using the
> memory? Are you using ZFS? Have you limited the vfs.zfs.arc_max to leave
> some free RAM for the bhyve instances?
> 
> -- 
> Allan Jude
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