Date: Mon, 7 Apr 2014 09:10:55 -0500 From: Mark Felder <feld@freebsd.org> To: freebsd-questions@freebsd.org Subject: Re: FreeBSD 10-R, Xen 4.1 guest, pf/NAT performance question Message-ID: <6876ba1714363dcbbdaf6b23f294fa2a@mail.feld.me> In-Reply-To: <CAJGy1F0aL=_U-P=wZDPc6tbKKke18PX-Ay8YUkj87=-pkXoAag@mail.gmail.com> References: <CAJGy1F0aL=_U-P=wZDPc6tbKKke18PX-Ay8YUkj87=-pkXoAag@mail.gmail.com>
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On 2014-04-07 07:57, seanrees@gmail.com wrote: > Hi there freebsd-questions, > > I've been batting my head against this problem for a few days now and > not > having much progress, so I'm hoping to get pointers at what to look at > next. > > I've got a FreeBSD 10-R guest in Xen 4.1 (I am just a customer of the > Xen > provider; I don't run the Xen hypervisor myself). I use this instance > to > terminate a VPN, for which I also NAT VPN clients with PF. I am seeing > unusually slow packet forwarding performance: 0.5mbit internet -> vpn > client, 2.0 mbit vpn client -> internet. (the numbers should be closer > to > 10mbit/5mbit). > > This guest is a duplicate of another Xen instance I have in another > data > centre. I manage the configurations and packages centrally and aside > from > IP address differences, the machines are configured identically. The > differences: it's 30ms closer to me and runs in Xen 3.4. I see > performance > from this machine in the 10mbps range. > > I've eliminated the obvious: > - The problem VPS is fine network wise; can download tarballs from > the > Internet at 100mbps. > - VPS -> Home is fine; can download at ~10mbps; the problem is > isolated > to forwarding Home -> VPS -> Internet and back. > - I excluded OpenVPN as the cause by replicating the setup with ssh > -w; > same performance. > - SSH port forwarding (ssh -L) is fast; indicating to me the issue is > somewhere in the PF/kernel. > - I checked TCP options by capturing traffic at varying points; these > seem fine. I see a good deal of TCP retransmits but the window sizes > stay > the same. > > Any thoughts on what to check next? > Have you turned off TSO? ifconfig xn0 -tso or sysctl net.inet.tcp.tso=0
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