Date: Fri, 29 Jan 2016 15:39:22 -0600 From: Xiaoye Sun <Xiaoye.Sun@rice.edu> To: Pavel Odintsov <pavel.odintsov@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: swaping ring slots between NIC ring and Host ring does not always success Message-ID: <CAJnByzirLXdCe-kwHV2s_E6ytGJG0Dth=0Ms12RrEk7FK_%2B8Og@mail.gmail.com> In-Reply-To: <CALgsdbd3XuE3wMYp4ey%2B1aer%2BHSVNojLYoVqwqTBPAXXdf9i%2BQ@mail.gmail.com> References: <CAJnByzj6Dj3vouZ2NbxqvCV-2-7TVtTR4FaWKuCFaaRN2X%2ByAA@mail.gmail.com> <CALgsdbd3XuE3wMYp4ey%2B1aer%2BHSVNojLYoVqwqTBPAXXdf9i%2BQ@mail.gmail.com>
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Hi Pavel, Our code is somewhat complicate. So I did a very simple experiment having the same problem so that you could regenerate the problem. In the new experiment, I used a very simple udp sender and udp receiver that sends and receives udp packet with seq num. I put the code here. http://www.owlnet.rice.edu/~xs6/receiver.c http://www.owlnet.rice.edu/~xs6/sender.c To repeat the experiment, on machine A, I run the sender program (command: sender 10.10.10.1 (your receiver IP)). On machien B, I run a netmap bridge that swap the slot printer between the host ring and the nic ring (the bridge example in netmap package /examples/bridge.c using the command ./bridge netmap:eth1 netmap:eth1) and also run the receiver program. I am able to see that the receiver print message saying that the new seq number is less than the seq number received in the previous round. Please let me know if you successfully generates the same problem. Thank! Xiaoye On Tue, Jan 26, 2016 at 1:53 AM, Pavel Odintsov <pavel.odintsov@gmail.com> wrote: > Hello! > > Really useful and detailed research. Thanks a lot! Could you share > your validation code? It could be useful for consistency tests for > netmap. > > So I could not help with your original question. Let's wait answer > from developers of awesome Netmap :) > > On Tue, Jan 26, 2016 at 2:55 AM, Xiaoye Sun <Xiaoye.Sun@rice.edu> wrote: > > Hi all, > > > > I wrote a netmap application that is very similar to bridge.c in > master/example > > directory of the netmap code. The major difference between my program and > > bridge.c is that my application also creates custom packets that are > > directly put into the tx ring of the NIC (like a packet generator with > > NIC-Host packet forwarding). Each generated packet has an unique sequence > > number so that the receiver can tell if a packet is lost. > > > > Like bridge.c, the packet forwarding between the nic and the host uses > > 'zerocopy', so that the program only swaps the buf_idx of the slots to > > virtually forward the packet to the other end. NS_BUF_CHANGED is set for > > the slots (both rx and tx) whose buf_idx has been changed due to > zerocopy. > > > > I set the number of rings on nic to 1 using the ethtool command, i.e., > one > > pair of netmap rings for the nic (one for host tx and one for host rx) > and > > another pair of rings for the host (one for host tx and one for host rx). > > > > However, at the receiver side, I found that there is a chance (very > little > > chance, less than 1% of the swaps) where swapping the buf_idx does not > > success. The receiver might get the packet in the buffer swapped out. For > > example, the netmap program wants to swap host slot *SH* with NIC slot > *SN* > > in order to send the packet in *SH* from host to the receiver; the > receiver > > might get the packet in *SN* instead. This usually happens to the very > end > > of the available slots. > > > > Our experiment is done on *Linux* machine (Linux 3.16.0-4-amd64 #1 SMP > > Debian 3.16.7-ckt11-1 (2015-05-24) x86_64 GNU/Linux) with* intel NIC* > > (Intel Corporation 82599ES 10-Gigabit SFI/SFP+ Network Connection) using > > the *ixgbe* driver. > > > > To understand this problem, I look into the patch code to the ixgbe > driver. > > I found that the flag NS_BUF_CHANGED is not used in the linux driver for > > ixgbe. please look the header file /LINUX/ixgbe_netmap_linux.h. In > funtions > > ixgbe_netmap_txsync and ixgbe_netmap_rxsync, the function call > > netmap_reload_map is commented out. However, the ixgbe's driver patch for > > FreeBSD calls the reload function. > > > > So, I am wondering if this is a known problem when using netmap on LINUX. > > Has anybody found the same problem? > > Is netmap_reload_map required in Linux? why it is not called in the > driver > > patch? > > What is the recommended solution for this problem? > > > > Thanks! > > > > Best, > > Xiaoye > > _______________________________________________ > > 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" > > > > -- > Sincerely yours, Pavel Odintsov > >
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