Date: Sat, 17 Mar 2018 08:19:52 +0100 From: Vincenzo Maffione <v.maffione@gmail.com> To: Joe Buehler <aspam@cox.net> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: netmap ixgbevf mtu Message-ID: <CA%2B_eA9jsegU%2BLPbzj5fQ9ADDxSz9ccy2m90V-0R2NLZR_6daSQ@mail.gmail.com> In-Reply-To: <5AAC4A96.1040107@cox.net> References: <5AAC49BE.3030508@cox.net> <5AAC4A96.1040107@cox.net>
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First, please make sure to use the latest netmap from github. Yes, drivers in general use 2K or 4K RX buffers regardless of the MTU or netmap buffer size. To receive a frame larger than the RX buffer size you need multiple netmap slots (as multiple descriptors are used by the hardware), looking at the NS_MOREFRAG flag. See the example code in utils/functional.c::rx_one(). Also TX may have per-slot limitations (e.g. due to the size of the NIC TX fifo), but this is usually > 9K, so using a single descriptor per packet should always be ok. However, you can also use multiple slots on the TX side (see utils/functional.c::tx_one()). You need to set the buf_size parameter to the RX buffer size. Currently we miss a mechanism for netmap to get the actual RX buffer size from the NIC driver, so we assume 4K. We need to check that buf_size is >= RX buffer size. This mechanism will be added soon. Cheers, Vincenzo 2018-03-16 23:52 GMT+01:00 Joe Buehler <aspam@cox.net>: > Sorry, I should have added, this is LINUX if it matters. > > Joe Buehler wrote: > > I am having difficulties with netmap over top of ixgbevf when attempting > to use a large MTU (say 9000 bytes). > > > > Does the ixgbevf driver use 2048 byte buffers for RX regardless of the > MTU or netmap buffer size? > > > > I can send large frames just fine but inbound frames are passed via > netmap as 2048 bytes max. It is possible that netmap is passing frames in > multiple pieces I suppose, I haven't checked that yet -- my code is looking > at the frame headers only at the moment so would toss trailing pieces. > > > > Joe Buehler > > > > > > _______________________________________________ > freebsd-net@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > -- Vincenzo Maffione
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