Am 13.05.2019 um 10:32:48 schrieb Michael Fritscher:
Good day,
Scenario:
Host: Windows 7 and 10 64 bit, Skylake+ CPUs
Qemu Version: 3.1 (4.0 isn't available yet on https://qemu.weilnetz.de/)
Accelerators: HAXM and WHPX
Guest: Ubuntu 18.04.2 64 bit, minimal install
Guest's tasks: OpenVPN, iptables, tc
Configuration:
-machine q35,accel=kvm:hvf:whpx:hax:tcg
-m 512
-smp 1
-rtc base=utc
-drive file=layertc_environmentmanager_amsvm.iso,if=virtio,media=cdrom
-vga std
-netdev
user,id=natted,
restrict=n,
net=172.31.1.0/255.255.255.0,
dhcpstart=172.31.1.1,
host=172.31.1.3,
dns=172.31.1.4
-device virtio-net,netdev=natted,mac=00:50:56:00:08:00
-nodefaults
-monitor tcp:localhost:4444
-kernel vmlinuz
-initrd initrd.img
-append "boot=casper textonly quiet nosplash nofb fb=false pti=off spectre_v2=off
l1tf=off nospec_store_bypass_disable noprompt"
(the iso is a casper livecd, but I start the linux kernel directly because of
boot speed)
Problem:
It is slow...
While a openssl speed -elapsed -evp aes-128-cbc is ok (500MB/sec and beyond),
OpenVPN struggles.
I get 70% virtual CPU usage , mostly on OpenVPN and system load while
transfering 1-2 MB/s with a UDP video stream. The measured delay is also
rather spiky and is about 30...40 ms. On the host I get a cpu usage of about
10% (=almost a core) I see this both on the server and the client
side.
On the player edition of the big commercial player, the results are _much_
better (10% virtual CPU usage, delay of 4-6 ms)
How can I further debug this? Do you know any knobs I can try? Slirp, while
there are warnings of being slow, doesn't seem to be the culprit as
I can get easily >>10 MB/s through it. And I see the big CPU usage of OpenVPN
Best regards,
Michael Fritscher
Hi again,
after a bit of digging, openVPN seems to call read_hpet with about 1 kHz, which
is, regarding to the program perf, the main culprit. Is a call
rate of this frequency normal and qemu is just very slow to handle them, or is
there another problem?
Best regards,
Michael Fritscher
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