Date: Tue, 2 Feb 2016 15:48:32 -0600 From: Xiaoye Sun <Xiaoye.Sun@rice.edu> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: Pavel Odintsov <pavel.odintsov@gmail.com>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: swaping ring slots between NIC ring and Host ring does not always success Message-ID: <CAJnByzh-VrRZeYdpkRFtCUGEN_arFBkemcN7byb51XV6UPswyg@mail.gmail.com> In-Reply-To: <CA%2BhQ2%2BhjnuGo1xKgc8CQ7gP35tiaZG7%2BroZBmX8aBgb8qWnLgg@mail.gmail.com> References: <CAJnByzj6Dj3vouZ2NbxqvCV-2-7TVtTR4FaWKuCFaaRN2X%2ByAA@mail.gmail.com> <CALgsdbd3XuE3wMYp4ey%2B1aer%2BHSVNojLYoVqwqTBPAXXdf9i%2BQ@mail.gmail.com> <CAJnByzirLXdCe-kwHV2s_E6ytGJG0Dth=0Ms12RrEk7FK_%2B8Og@mail.gmail.com> <CA%2BhQ2%2BgMWY0eabjHGw0=PJCAkS-wO=RBrN5brSbaqWc3_AOYoQ@mail.gmail.com> <CAJnByziBS8o6LtmpUrUu5xtRUd008Z2hnCsp=WVFv35r2J0rHw@mail.gmail.com> <CA%2BhQ2%2Bim9nFfYnqDS2HgRbAzdf5D0iaLCmCYhfXQVVRMouUFuw@mail.gmail.com> <CAJnByzht-qfDcm8oEg1aSRyVBZ1ygPvc2eMuoyJcq4geueTZ0Q@mail.gmail.com> <CA%2BhQ2%2BiERgWJ=cdFB-cByfT3r11T1kKr-5HiuCYZY-rxbjf=XA@mail.gmail.com> <CAJnByziDzdR2C6DcSRNPtrWACLq0XFpe4X1Ek9yXtFP9ivqWQw@mail.gmail.com> <CA%2BhQ2%2BhjnuGo1xKgc8CQ7gP35tiaZG7%2BroZBmX8aBgb8qWnLgg@mail.gmail.com>
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On Mon, Feb 1, 2016 at 11:34 PM, Luigi Rizzo <rizzo@iet.unipi.it> wrote: > On Tue, Feb 2, 2016 at 6:23 AM, Xiaoye Sun <Xiaoye.Sun@rice.edu> wrote: > > Hi Luigi, > > > > I have to clarify about the *jumping issue* about the slot indexes. > > In the bridge.c program, the slot index never jumps and it increases > > sequentially. > > In the receiver.c program, the udp packet seq jumps and I showed the slot > > index that each udp packet uses. So the slot index jumps together with > the > > udp seq (at the receiver program only). > > So let me understand, is the "slot" some information written > in the packet by bridge.c (referring to the rx or tx slot, > I am not sure) and then read and printed by receiver.c > (which gets the packet through recvfrom so there isn't > really any slot index) ? > > It works in the other way: The bridge.c checks the seq numbers of the udp packets in netmap slots (in nic rx ring) before the swap; then it records the seq number, slot number(both rx and tx (tx indexes were not shown in the previous email since they all look correct)) and buf_idx (rx and tx). The bridge.c does not change anything in the buffer and it knows the slot and buf_idx that a packet uses. Please refer to the added code in *process_rings* function http://www.owlnet.rice.edu/~xs6/bridge.c The receiver.c checks the seq numbers only and print out the seq numbers it receive sequentially. With these information, I manually match the seq number I got from receiver.c and the seq number I got from bridge.c. So we know what is the seq order the receiver sees and which slot a packet uses when bridge.c swaps the buf_idxs. Do you see any ordering inversion when the receiver > gets packets through the NETMAP API (e.g. using bridge.c > instead of receiver.c) ? > > There is no ordering inversion seen by bridge.c (As I said in the previous paragraph, the bridge.c checks the seq number and I did not see any order inversion in THIS simple experiment (In my multicast protocol (mentioned in the first email), there is ordering inversion. But let us solve the simple bridge.c's problem first. I think they are two relatively independent issues.)). > Are you using native netmap drivers or the emulated mode ? > You can check that by playing with the "admode" sysctl entry > (or sysfs on linux) - try setting to 1 and 2 and see if > the behaviour changes. > > dev.netmap.admode: 0 > Controls the use of native or emulated adapter mode. > 0 uses the best available option, > 1 forces native and fails if not available, > 2 forces emulated hence never fails. > > I was using admode 0. I changed the admode to 1 and 2 using the command like *echo 1 > /sys/module/netmap/parameters/admode* and restart the bridge program. The behavior keeps the same. > cheers > luigi > > > > > There is really one ring (tx and rx) for NIC and one ring (tx and rx) for > > the host. > > I also doubt that there might be multiple tx rings for the host. It seems > > like that bridge program swap packet to multiple host rings and the udp > recv > > program drains packets from these rings. But this is not the case here. > > > > The bridge program prints a line like this > > *515.277263 main [277] Ready to go, eth3 0x1/1 <-> eth3 0x0/1.* > > this is printed by the following line the original program > > *D("Ready to go, %s 0x%x/%d <-> %s 0x%x/%d.", pa->req.nr_name, > > pa->first_rx_ring, pa->req.nr_rx_rings, pb->req.nr_name, > pb->first_rx_ring, > > pb->req.nr_rx_rings);* > > > > I think this shows that there is really one NIC ring and one HOST ring. > > > > Is there another way to verify the number of ring that netmap has? > > > > Thanks! > > Xiaoye > > > > On Mon, Feb 1, 2016 at 10:48 PM, Luigi Rizzo <rizzo@iet.unipi.it> wrote: > >> > >> Hi, > >> there must be some wrong with your setting because > >> slot indexes must be sequential and in your case they > >> are not (see the jump from 295 to 474 and then > >> back from 485 to 296, and the numerous interleavings > >> that you are seeing later). > >> > >> I have no idea of the cause but typically this pattern > >> is what you see when there are multiple input rings and > >> not just one. > >> > >> Cheers > >> Luigi > >> > >> > >> > >> > >> On Tue, Feb 2, 2016 at 12:24 AM, Xiaoye Sun <Xiaoye.Sun@rice.edu> > wrote: > >> > Hi Luigi, > >> > > >> > Thanks for the detailed advice. > >> > > >> > With more detailed experiments, actually I found that the udp > >> > sender/receiver packet reorder issue *might* be irrelevant to the > >> > original > >> > issue I posted. However, I think we should solve the udp > sender/receiver > >> > issue first. > >> > I run the experiment with more detailed log. Here is my findings. > >> > > >> > 1. I am running a netmap version available since about Oct 13rd from > >> > github > >> > (https://github.com/luigirizzo/netmap). So I think this is not the > one > >> > related to the buffer allocation issue. I tried to running the newest > >> > version, however, that version causes problem when I exit the bridge > >> > program > >> > (something like kernel error which make the os crash). > >> > > >> > 2 & 3. I changed the receiver.c & bridge.c so that I can get more > >> > information (more detailed log). > >> > The reorder happens multiple times (about 10 times) within a second. > >> > Here is > >> > one example trace collected from the above two programs. (remembering > >> > that > >> > we have udp sender running on one machine; netmap bridge and udp > >> > receiver > >> > are running on another machine). > >> > There is only one pair of rings each with 512 slots (511 slot usable) > on > >> > the > >> > receiver machine. > >> > > >> > =================== packet trace collected from receiver.c > >> > =================== > >> > ===== together with the slot and buf_idx of the corresponding netmap > >> > ring > >> > slots ====== > >> > [seq] [slot] [buf_idx] > >> > 8208 294 1833 > >> > 8209 295 1834 > >> > 8388 474 2013 > >> > ... (packet received in order) > >> > 8398 484 2023 > >> > 8399 485 2024 > >> > 8210 296 1835 > >> > 8211 297 1836 > >> > ... (packet received in order) > >> > ... > >> > 8222 308 1847 > >> > 8400 486 2025 > >> > 8223 309 1848 > >> > 8401 487 2026 > >> > 8224 310 1849 > >> > 8402 488 2027 > >> > 8225 311 1850 > >> > 8403 489 2028 > >> > 8226 312 1851 > >> > 8404 450 2029 > >> > 8227 313 1852 > >> > 8228 314 1853 > >> > =================================================================== > >> > As we can see that the udp receiver got packet 8210 after it got 8399, > >> > which > >> > is the first reorder. Then, the receiver got 8211 to 8222 > sequentially. > >> > Then > >> > it got packet from 8223-8227 and 8400-8404 interleaved. > >> > > >> > > >> > ==================== event order seen by netmap bridge > >> > ================== > >> > get 8209 > >> > poll called > >> > get 8210 > >> > ... > >> > ... > >> > get 8228 > >> > poll called > >> > get 8229 > >> > ... > >> > ... > >> > get 8383 > >> > poll called > >> > get 8384 > >> > ... > >> > get 8387 > >> > poll called > >> > get 8388 > >> > ... > >> > get 8393 > >> > poll called > >> > get 8394 > >> > ... > >> > get 8399 > >> > poll called > >> > get 8400 > >> > ... > >> > get 8404 > >> > poll called > >> > get 8405 > >> > =================================================================== > >> > As we can see, from the event ordering see by the bridge.c, all the > >> > packets > >> > are receiver in order, which means the the reorder happens when the > >> > bridge > >> > code swap the buf_idx between the nic ring(slot) and the host > >> > ring(slot). > >> > The reordered seq usually right before or after the poll function > call. > >> > > >> > Best, > >> > Xiaoye > >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> > On Fri, Jan 29, 2016 at 4:27 PM, Luigi Rizzo <rizzo@iet.unipi.it> > wrote: > >> >> > >> >> On Fri, Jan 29, 2016 at 2:12 PM, Xiaoye Sun <Xiaoye.Sun@rice.edu> > >> >> wrote: > >> >> > Hi Luigi, > >> >> > > >> >> > Thanks for your advice. > >> >> > I forgot to mention that I use the command "ethtool -L eth1 > combined > >> >> > 1" > >> >> > to > >> >> > set the number of rings of the nic to 1. The host also only has > one > >> >> > ring. > >> >> > I understand the situation where the first tx ring is full so the > >> >> > bridge > >> >> > will swap the packets to the second tx ring and then the host/nic > >> >> > might > >> >> > drain either rings. But this is not the case in the experiment. > >> >> > >> >> ok good to know that. > >> >> > >> >> So if we have ruled out multiqueue and iommu, let's look at > >> >> the internal allocator and at bridge.c > >> >> > >> >> 1. are you running the most recent version of netmap ? > >> >> Some older version (probably 1-2 years ago) had a bug > >> >> in the buffer allocator and some buffers were allocated > >> >> twice. > >> >> > >> >> 2. can you tweak your receiver.c to report some more info > >> >> on how often you get out of sequence packets, how much > >> >> out of sequence they are ? > >> >> Also it would be useful to report gaps on the increasing side > >> >> (i.e. new_seq != old_seq +1 ) > >> >> > >> >> 3. can you tweak bridge.c so that it writes into the packet > >> >> the netmap buffer indexes and slots on the rx and tx side, > >> >> so when you detect a sequence error we can figure out > >> >> where it is happening. > >> >> Ideally you could also add the sequence number detection > >> >> code in bridge.c so we can check whether the errors appear > >> >> on the input or output sides. > >> >> > >> >> cheers > >> >> luigi > >> >> > >> > > >> > >> > >> > >> -- > >> > -----------------------------------------+------------------------------- > >> Prof. Luigi RIZZO, rizzo@iet.unipi.it . Dip. di Ing. > dell'Informazione > >> http://www.iet.unipi.it/~luigi/ . Universita` di Pisa > >> TEL +39-050-2217533 . via Diotisalvi 2 > >> Mobile +39-338-6809875 . 56122 PISA (Italy) > >> > -----------------------------------------+------------------------------- > >> > > > > > > -- > -----------------------------------------+------------------------------- > Prof. Luigi RIZZO, rizzo@iet.unipi.it . Dip. di Ing. dell'Informazione > http://www.iet.unipi.it/~luigi/ . Universita` di Pisa > TEL +39-050-2217533 . via Diotisalvi 2 > Mobile +39-338-6809875 . 56122 PISA (Italy) > -----------------------------------------+------------------------------- > >
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