Red Hat Bugzilla – Bug 1006742
Poor performance using kvm with fully virtualized network (e1000).
Last modified: 2013-09-19 01:50:59 EDT
Description of problem:
Network speed on fully virtualized network card (for example e1000) is very slow in KVM guests. Same problems on multiple dell servers. The use bnx2 network card driver. Switching to virtio in guest will fix this problem.
Version-Release number of selected component (if applicable):
All 3.10.* kernels:
Steps to Reproduce:
1. boot Fedora KVM host with 3.10.* kernel (or maybe higher)
2. install KVM guest with netcard <model type='e1000'/>
3. run in guest: wget -O /dev/null ftp://host/large_file
not more than 10MB/s transfer with kernels 3.10.*
Average speed should be in kB/s.
Transfer at least at 30MB/s.
Changing guest netcard to virtio fixes my problems, so this looks to be not an host physical network card problem.
Also rebooting host to 3.9 kernel fixes this problem, so it's not a network problem.
I have same problem with 2 different DELL machines, which use bnx2 network card. Unable to reproduce with my noname workstation with Fedora and kernel3.10.
Tested also fully virtualized disk, where speeds are slower (virtio 150MB/s, IDE 110MB/s) but not so much. I think it's expected, that virtio should be faster.
Does not matter, which guest OS is installed, same problem with Fedora and Windows.
so just in order to get a very clear picture:
A) Host kernel with kernel-3.9.5-301.fc19.x86_64 and guest with fully
emulated e1000 network card gives you a ~30MB/s
B) Exact same host but with kernel-3.10.x and with the exact same guest with
e1000 network card gives you ~10MB/s
Is my understanding correct? So no other changes on the host except the kernel and the guest is always the same, right?
What kernel/fedora version does the guest use?
Here are some tests. There is host kernel version and still same guest network configuration:
host 3.9.5-301.fc19.x86_64, guest: <model type='e1000'/>
100%[======================>] 4,519,362,560 58.8M/s in 74s
2013-09-12 07:51:16 (58.2 MB/s) - `/dev/null' saved 
host 3.9.5-301.fc19.x86_64, guest: <model type='virtio'/>
100%[======================>] 4,519,362,560 59.6M/s in 72s
2013-09-12 07:54:12 (60.1 MB/s) - `/dev/null' saved 
host 3.10.9-100.fc18.x86_64, guest: <model type='virtio'/>
100%[======================>] 4,519,362,560 60.5M/s in 71s
2013-09-12 09:48:07 (60.6 MB/s) - `/dev/null' saved 
host 3.10.9-100.fc18.x86_64, guest: <model type='e1000'/>
0% [ ] 1,664,856 139K/s eta 21h 43m
host 3.10.10-200.fc19.x86_64, guest: <model type='virtio'/>
100%[======================>] 4,519,362,560 60.2M/s in 73s
2013-09-12 10:59:20 (58.8 MB/s) - `/dev/null' saved 
host 3.10.10-200.fc19.x86_64, guest: <model type='e1000'/>
0% [ ] 674,424 64.6K/s eta 23h 17m
host 3.10.10-200.fc19.x86_64, host speed for comparison
100%[======================>] 4,519,362,560 61.1MB/s in 70s
2013-09-12 08:24:39 (61.2 MB/s) - '/dev/null' saved 
Linux vpn-server 3.6.11-4.fc16.x86_64 #1 SMP Tue Jan 8 20:57:42 UTC 2013
x86_64 x86_64 x86_64 GNU/Linux
This is one of my old testing guests, but same problem with newer guests too.
And also same problem for windows guests.
wget -O /dev/null \
*********** MASS BUG UPDATE **************
We apologize for the inconvenience. There is a large number of bugs to go through and several of them have gone stale. Due to this, we are doing a mass bug update across all of the Fedora 19 kernel bugs.
Fedora 19 has now been rebased to 3.11.1-200.fc19. Please test this kernel update and let us know if you issue has been resolved or if it is still present with the newer kernel.
If you experience different issues, please open a new bug report for those.
Unable to reproduce with kernel 3.11.1-200.fc19.x86_64. Looks like it's fixed. Closing bug. Reopen if you consider to fix this for Fedora 18. I can't test on Fedora 18. Thank you for fix.