Also i have noticed, when TSO is disabled IPv4 TCP Performance also drops from
~10 Gb/s to ~3 Gb/s, the same as with IPv6. I have read threads from around
2010 about the networking stack not having support for TSO on IPv6 Packets. May
this be the problem in this case?
> On 14 Jul 2015, at 23:44, Sydney Meyer <syd.me...@gmail.com> wrote:
>> On 14 Jul 2015, at 18:15, Mark Felder <f...@freebsd.org> wrote:
>> On Tue, Jul 14, 2015, at 07:36, Sydney Meyer wrote:
>>> Hello everybody,
>>> i have noticed some odd behaviour with networking under Xen with FreeBSD
>>> 10 as a DomU.
>>> - IPv6 (TCP) bandwith drops from ~10 Gbit/s IPv4 to around 3 Gbit/s IPv6.
>>> (measured with iperf)
>> What is the "before" and "after" here? When is FreeBSD successfully
>> doing 10Gbit/s and when isn't it? Is pf enabled? Are you scrubbing?
> With two clean 10.1 AMD64 DomU installations both with a single, pinned cpu,
> without pf enabled the TCP performance between the two hosts, measured with
> iperf, differs between ~10 Gb/s on IPv4 and ~3 Gb/s on IPv6. With pf enabled
> and "scrub in all" the difference is almost the same.
>>> - Dropped/Stalled Connections with TCP Segmentation Offload and pf
>> TSO is a known issue. I've been turning it off for years to get FreeBSD
>> to play nice on Xen.
> This one i am still investigating, because it happens only in "certain"
> situations (which are not clear to me, atm), but the host seems to drop ACK
> Packets in some situations like when connected to via IPSEC or via double
> NAT. This happens only when pf it actually enabled. Disabling TSO on the
> xn-interface seems to help.
>>> - IPSEC-enabled Kernel TCP Performance drops from ~10 Gbit/s to ~200
>>> Mbit/s (iperf).
>> Are you saying FreeBSD non-IPSEC kernel can do 10Gbit/s TCP performance,
>> but IPSEC kernel immediately drops it to 200Mbit/s?
> As for the apparent performance drop with IPSEC enabled Kernels without
> security associations installed, i am unable to reproduce this now, not on
> 10.0 or 10.1 nor 10 STABLE. Only when actually _using_ IPSec the performance
> drops from ~10Gb/s to around ~200Mb/s whether actually encrypting esp traffic
> or not.
> This clearly must have been a mistake on my side, although i could have sworn
> that i checked this two times before asking on the forums and the -net
> mailing list a few weeks ago. Well then, i am sincerely sorry about this one.
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