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Re: [Qemu-devel] Contribution - L2TPv3 transport
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] Contribution - L2TPv3 transport |
Date: |
Mon, 3 Mar 2014 14:27:46 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Fri, Feb 28, 2014 at 08:28:11AM +0000, Anton Ivanov (antivano) wrote:
> 3. Qemu to communicate with the local host, remote vms, network devices,
> etc at speeds which for a number of use cases exceed the speed of the
> legacy tap driver.
This surprises me. It's odd that tap performs significantly worse.
I guess you have two options for using kernel L2TPv3 support:
1. Use a bridge and tap to forward between the L2TPv3 interface and the
QEMU.
2. Use macvtap on top of the L2TPv3 interface (if possible).
Option #2 should be faster.
Now about the tap userspace ABI, is the performance bottleneck that the
read(2) system call only receives one packet at a time? The tap file
descriptor is not a socket so recvmmsg(2) cannot be used on it directly.
I have wondered in the past whether something like packet mmap would be
possible on a tap device. At that point userspace just waits for
notifications and the actual packets don't require any syscalls.
> Our suggestion would be that this over time obsoletes the UDP variety of
> the "socket" driver.
Yes, thank you! L2TPv3 looks like a good replacement for the "socket"
driver.
Will review and respond to your patch in detail.
Stefan
- Re: [Qemu-devel] Contribution - L2TPv3 transport,
Stefan Hajnoczi <=