bhyve uses all available memory during IO-intensive operations
Dustin Wenz
dustinwenz at ebureau.com
Fri Dec 1 17:43:02 UTC 2017
Here's the top -uS output from a test this morning:
last pid: 57375; load averages: 8.29, 7.02, 4.05 up 38+22:19:14 11:28:25
68 processes: 2 running, 65 sleeping, 1 waiting
CPU: 0.1% user, 0.0% nice, 40.4% system, 0.4% interrupt, 59.1% idle
Mem: 2188K Active, 4K Inact, 62G Wired, 449M Free
ARC: 7947M Total, 58M MFU, 3364M MRU, 1000M Anon, 2620M Header, 904M Other
4070M Compressed, 4658M Uncompressed, 1.14:1 Ratio
Swap: 112G Total, 78M Used, 112G Free, 4K In, 12K Out
PID UID THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND
11 0 24 155 ki31 0K 384K RUN 0 ??? 1446.82% idle
0 0 644 -16 - 0K 10304K swapin 21 554:59 492.45% kernel
57333 0 30 20 0 17445M 1325M kqread 9 16:38 357.42% bhyve
15 0 10 -8 - 0K 192K arc_re 20 80:54 81.55% zfskern
5 0 6 -16 - 0K 96K - 5 12:35 11.50% cam
12 0 53 -60 - 0K 848K WAIT 21 74:35 9.40% intr
41094 0 30 20 0 17445M 14587M kqread 17 301:29 0.39% bhyve
Dec 1 11:29:31 <kern.err> service014 kernel: pid 57333 (bhyve), uid 0, was killed: out of swap space
Dec 1 11:29:31 <kern.err> service014 kernel: pid 69549 (bhyve), uid 0, was killed: out of swap space
Dec 1 11:29:31 <kern.err> service014 kernel: pid 41094 (bhyve), uid 0, was killed: out of swap space
This was with three VMs running, but only one of them was doing any IO. Note that the whole machine hung for about about 60 seconds before the VMs were shut down and memory recovered. That's why the top output is over a minute older than the kill messages (top had stopped refreshing).
What I'm suspicious of is that almost all of the physical memory is wired. If that is bhyve memory, why did it not page out?
- .Dustin
> On Nov 30, 2017, at 5:15 PM, Dustin Wenz <dustinwenz at ebureau.com> 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
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