[PVE-User] high cpu load on 100mbits/sec download with virtio nic

[Josh Knight]

I'm not convinced this is a proxmox issue, or even an issue to begin with.

I'm running proxmox 5.1-49, in my Linux 4.1 guest when I run wget -O
/dev/null <https to ~1.2GB iso> I'm seeing ~30% according to top as well.

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
12788 root      20   0   65512   7616   5988 S  31.3  0.1   0:03.00 wget


Even on a physical box running Ubuntu I'm getting around 20-30% or more.

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
36070 root      20   0   32888   4028   3576 S  37.6  0.0   0:03.15 wget


This could be an issue/quirk with the way top is calculating cpu usage, or
it's just a process using available cpu as normal. I couldn't reproduce
high load using ping -f from a remote host to my VM, and iotop confirmed
that -O /dev/null wasn't somehow writing to disk.  I was able to lower the
CPU usage by running wget with --limit-rate=.

Related, I would not recommend macvtap if you're running routers.  At least
running on an Ubuntu 16.04 host, under load of ~1Gb we were seeing anywhere
from 0.01% to 0.16% packet loss before it reached the guest's virtio
interface.  We switched to linux bridge and then finally to openvswitch
with the default switching config (no custom openflow rules.)


Josh Knight


On Thu, Jun 7, 2018 at 11:44 AM, Maxime AUGER <m.auger at auranext.com> wrote:

> Thank you for your statement
>
> I wget on the debian8 GUEST
>
> -> GUEST-CPU = 25% of 1x vcpu
> -> HOST-CPU = 30% of 2x cores (each one)
>
> Ex with "-O /dev/null" : host TOP (the cpu decreases a little bit)
>   PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND
>  6833 root      20   0 1972312 892460   5900 S 31.1 43.7 184:54.60
> /usr/bin/kvm -id 108 -name fg-v4-bench-8 -chardev
> socket,id=qmp,path=/var/run/qemu-server/108.qmp,server,nowait -mon
> chardev=qmp,mode=control -pidfile /var/run/qemu-server/108.pid -daemonize
> -smbios type=1,uuid=b1572470-0605-44da-9bae-0b2a6d43954a -s+
>  6772 root      20   0       0      0      0 R 11.9  0.0   1:37.54
> [vhost-6712]
>
>
>
>  6834 root      20   0 1972312 892460   5900 S  7.9 43.7 173:24.10
> /usr/bin/kvm -id 108 -name fg-v4-bench-8 -chardev
> socket,id=qmp,path=/var/run/qemu-server/108.qmp,server,nowait -mon
> chardev=qmp,mode=control -pidfile /var/run/qemu-server/108.pid -daemonize
> -smbios type=1,uuid=b1572470-0605-44da-9bae-0b2a6d43954a -s+
>  6712 root      20   0 1972312 892460   5900 S  1.3 43.7   7:50.63
> /usr/bin/kvm -id 108 -name fg-v4-bench-8 -chardev
> socket,id=qmp,path=/var/run/qemu-server/108.qmp,server,nowait -mon
> chardev=qmp,mode=control -pidfile /var/run/qemu-server/108.pid -daemonize
> -smbios type=1,uuid=b1572470-0605-44da-9bae-0b2a6d43954a -s+
>
>
>
>
> -----Message d'origine-----
> De : pve-user [mailto:pve-user-bounces at pve.proxmox.com] De la part de
> Mark Schouten
> Envoyé : jeudi 7 juin 2018 17:03
> À : PVE User List <pve-user at pve.proxmox.com>
> Objet : Re: [PVE-User] high cpu load on 100mbits/sec download with virtio
> nic
>
> On Thu, 2018-06-07 at 14:49 +0000, Maxime AUGER wrote:
> > I'm doubtful about the performance I get.
> >
> > On proxmox HOST a single wget download consume 12% single CPU load at
> > 11MBytes/sec (1518 packets size)
>
> Where are you wgetting to? Benchmarking this is better with iperf or so.
>
> If you want to wget, do wget -O /dev/null so you're not suffering from
> diskperformance..
>
> --
> Kerio Operator in de Cloud? https://www.kerioindecloud.nl/ Mark Schouten
> | Tuxis Internet Engineering
> KvK: 61527076  | http://www.tuxis.nl/
> T: 0318 200208 | info at tuxis.nl
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