Date: Fri, 19 Sep 2014 09:02:40 +1200 From: mailinglists@debank.tv To: freebsd-net@freebsd.org, owner-freebsd-net@freebsd.org Cc: Bryan Venteicher <bryanv@daemoninthecloset.org> Subject: Re: Performance problem with slow link behind fast gateway (solved: worked around) Message-ID: <cd09da7735c0a1538cda224f64639286@debank.tv> In-Reply-To: <CAMo0n6RRTAD_NSjT-b96paoBXz%2BV11Xx4gRTyVrSondeL_NjCw@mail.gmail.com> References: <a5d07d35c0e3f423e6782410a175fcd2@debank.tv> <CAMo0n6RRTAD_NSjT-b96paoBXz%2BV11Xx4gRTyVrSondeL_NjCw@mail.gmail.com>
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On 2014-09-15 07:55, Bryan Venteicher wrote: > Hi, > > On Tue, Sep 9, 2014 at 4:42 PM, <mailinglists@debank.tv> wrote: > >> All, >> >> I'm seeing some performance problems with a slowish VPN connection >> behind >> a fast gateway, the setup looks like this: >> >> |----------------------------------| >> |-----------------------------| >> |client (zandbak) (DSL connection)| ---- 'VPN tunnel' ----- |Gateway >> (vps) using NAT on 1G|------ 'Internet' >> |----------------------------------| >> |-----------------------------| >> >> >> Transfers from the gateway to the client are reasonably fast (easily >> within usable range for me): >> root@zandbak:/usr/home/rob # scp rob@gateway:test_file ./ >> test_file >> 100% 10MB 445.2KB/s 00:23 >> >> >> Transfers from the internet to the gateway are fast: >> root@vps:/usr/home/rob # fetch -4 "http://149.20.53.23/pub/ >> FreeBSD/releases/amd64/amd64/ISO-IMAGES/10.0/FreeBSD-10.0- >> RELEASE-amd64-bootonly.iso" >> FreeBSD-10.0-RELEASE-amd64-bootonly.iso 100% of 209 MB 10 >> MBps >> 00m20s >> >> >> But transfers from the client to the internet through the tunnel are >> showing a very degraded connection speed, the speed jumps up and down >> but >> averages at around 20kBps: >> root@zandbak:/usr/home/rob # fetch "http://149.20.53.23/pub/ >> FreeBSD/ISO-IMAGES-amd64/10.0/FreeBSD-10.0-RELEASE-amd64-bootonly.iso" >> FreeBSD-10.0-RELEASE-amd64-bootonly.iso 0% of 209 MB 8275 >> Bps >> 07h27m >> >> >> I've tried to eliminate some variables: >> -VPN: tinc as a L2 VPN and openVPN as a L3 VPN, results are the same >> -NAT: pf and ipfw, results are the same >> >> I suspect that there's a problem with the fast link receiving too much >> data and once the buffers are full dropping packets although I'm not >> sure >> if this is actually the problem. >> My question is: how can I debug this issue? >> >> >> > On the vtnet0 interface in your KVM VM, disable checksum offloading. > What > KVM/QEMU VirtIO provides as the "checksum" in situation likes this does > not > work well with what FreeBSD expects. Fixing this has been on my todo > list > for awhile, but it is a moderate amount of work to fix this, and > touches > many places in the stack. I have plans to do mbuf related work later > this > year, and was planning to finally fix this issue as well. > > > <--------------SNIP-----------> Thanks Bryan, I can confirm performance with checksum offloading disabled on the vtnet interface is back to expected levels! Rob Evers
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