Date: Thu, 26 Oct 2017 17:12:24 +0200 From: Vincenzo Maffione <v.maffione@gmail.com> To: Joe Buehler <aspam@cox.net> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: virtio_net / netmap RX dropping frames Message-ID: <CA%2B_eA9gbfGNJVAekB1f3VB-hghiaESUp_Ua5ZmHhhs9dKmvgYg@mail.gmail.com> In-Reply-To: <59F1F1BA.3020608@cox.net> References: <59F0FBEE.6030008@cox.net> <59F1F1BA.3020608@cox.net>
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So you are using netmap only in the guest (and not in the host). And you are running a sender and a receiver inside the VM, both on the VM interface. Something like this # pkt-gen -i eth1 -f rx # pkt-gen -i eth1 -f tx ? What happens if you use pkt-gen rather than your application? 2017-10-26 16:31 GMT+02:00 Joe Buehler <aspam@cox.net>: > Vincenzo Maffione wrote: > > I guess you are using a FreeBSD guest. Is this the case? If you have the > > Sorry, I am using LINUX, ubuntu 16.04 LTS for both host and VM. I am > posting here at standing request of netmap driver author. > > The host has 24 CPUs @ 2.5 GHz and 128G of memory and is *idle* so I am > a bit disappointed > > > chance, try a linux guest to check if virtio-net works better there > > (I've used netmap on the netmap-patched virtio-net in Linux guests, > > never tried on FreeBSD). > > The netmap ring size is just the NIC ring size. If you change the > > virtio-net NIC ring size (sysctl on FreeBSD, I guess). > > OK I'll look into that. I increased the ring size on the host ixgbe but > that had no effect so I guess it must be virtio_net. > > > Anyway, for your specific use-case (VM accessing the physical 10G NIC) > > there is a way better solution, which is the netmap passthrough. > > Unfortunately I don't have control of the host, just the VM, so pt > netmap is not an option. > > My initial query regarded frame drops but the latency is also pretty > bad. The LINUX ping utility inside the VM says 0.2 mS consistently > without netmap in use. My app sees that value for almost all frames but > it spikes (up to 0.6 mS!) for a few frames, which is not acceptable for > this application -- was expecting much better due to network stack > bypass. And this is just 100 frames/sec... > > Joe Buehler > -- Vincenzo Maffione
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