Date: Sat, 19 Apr 2014 14:17:32 +0100 From: "seanrees@gmail.com" <seanrees@gmail.com> To: Tiago Ribeiro <shasty@gmail.com> Cc: "freebsd-xen@freebsd.org" <freebsd-xen@freebsd.org> Subject: Re: VM in Xen 4.1; poor packet forwarding performance on xn0 Message-ID: <CAJGy1F2oQDXYzeFp3cT2ZMf=AhmL5b%2B0NHZhzaYA55XvZ4_MAA@mail.gmail.com> In-Reply-To: <2C3A747F-DA88-4815-A930-7C5EB1CD6238@gmail.com> References: <CAJGy1F0%2BG1zq9hVbifTM2Vq6HHEmCM9hnFvQ=4t-4d5x=npaCA@mail.gmail.com> <2C3A747F-DA88-4815-A930-7C5EB1CD6238@gmail.com>
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On Sat, Apr 19, 2014 at 1:11 PM, Tiago Ribeiro <shasty@gmail.com> wrote: > > > > Em 18/04/2014, =C3=A0s 11:57, "seanrees@gmail.com" <seanrees@gmail.com> > escreveu: > > > > Hi there freebsd-xen, > > > > I tried first on freebsd-questions@ without success, so I thought to > retry > > here. > > > > I run OpenVPN on a FreeBSD 10.0-Rp1 VM in Xen 4.1 (HVM). I am > experiencing > > slow network performance on xn0 that seems to have developed after I > > upgraded to FreeBSD 10 (no other changes). I can only achieve about > 0.5mbps > > through this interface when forwarding packets; packets in a single > > direction are fine (e.g; downloading to the VPS or pushing from the VPS= ) > > and clock in at many (>10 usually) mbps. > > > > Interestingly, my identical VM (configuration managed centrally) runnin= g > on > > Xen 3.4 (HVM) does *not* have this issue. > > > > I did a little debugging and here's what I've noticed: > > - Not related to OpenVPN, repro'd using ssh -d. > > - Slow VM has a very low rate of context switches (~250) while > > forwarding, fast VM has a lot more (~2000) sampled over 5 seconds using > > systat -v. > > - I can't repro a context switch limit (tried a limited fork() bomb). > > - Tried with *and* without LRO and TSO on xn0 (and all combinations of > > LRO and TSO on/off) > > > > I started digging into the Xen drivers but I realised I am not equipped > to > > debug this. I'm looking for suggestions on what to check. My provider i= s > > offering to move me to an older Xen host but I'd like to see if I can > help > > identify a bug either in my configuration or perhaps in FreeBSD's Xen > code. > > > > Sean > > _____________________________________________ > > > Do you use pf? I do. Fairly simple ruleset: default deny, a few specific port allows, NAT. Sean
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