From: Ingo Krabbe <ikrabbe.ask@gmail.com>
To: qemu-devel@nongnu.org
Subject: [Qemu-devel] TCP Segementation Offloading
Date: Sun, 1 May 2016 14:31:57 +0200 [thread overview]
Message-ID: <404102019afadcf28f8dcb958fcbf617@yourdomain.dom> (raw)
Good Mayday Qemu Developers,
today I tried to find a reference to a networking problem, that seems to be of quite general nature: TCP Segmentation Offloading (TSO) in virtual environments.
When I setup TAP network adapter for a virtual machine and put it into a host bridge, the known best practice is to manually set "tso off gso off" with ethtool, for the guest driver if I use a hardware emulation, such as e1000 and/or "tso off gso off" for the host driver and/or for the bridge adapter, if I use the virtio driver, as otherwise you experience (sometimes?) performance problems or even lost packages.
I haven't found a complete analysis of the background of these problems, but there seem to be some effects on MTU based fragmentation and UDP checksums.
There is a tso related bug on launchpad, but the context of this bug is too narrow, for the generality of the problem.
Also it seems that there is a problem in LXC contexts too (I found such a reference, without detailed description in a Post about Xen setup).
My question now is: Is there a bug in the driver code and shouldn't this be documented somewhere in wiki.qemu.org? Where there developments about this topic in the past or is there any planned/ongoing work todo on the qemu drivers?
Most problem reports found relate to deprecated Centos6 qemu-kvm packages.
In our company we have similar or even worse problems with Centos7 hosts and guest machines.
I'm going to analyze these problems next week anyway and I woud be happy to share my observation with you. (Where can I register for the wiki, or whom should I sent my reports about this topic?).
Regards,
Ingo Krabbe
next reply other threads:[~2016-05-01 12:32 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-01 12:31 Ingo Krabbe [this message]
2016-05-05 17:42 ` [Qemu-devel] TCP Segementation Offloading Stefan Hajnoczi
2016-05-06 4:34 ` Ingo Krabbe
2016-05-06 16:28 ` Stefan Hajnoczi
2016-05-09 12:12 ` Michael S. Tsirkin
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