Hi Marcus, spb(=samples/buffer) is not what I hoped for. It is just another way to set the stream_cmd.num_samples in the streamer. I already use there MAXSMPS. Besides benchmark_rate reports maxsmps 1996 like me:( That part is only controlled by the MTU. Seems it is the same for everyone, and that we are using the generic chdr_sc16_to_xx instead the guts (sse2) conversion:( Unless they use the multi_usrp class and set spp on their own. I think that MAXSMPS used to be 1996, before someone changed it to 19960.
BR Nikos BR Nikos On Mon, Apr 28, 2025 at 5:22 PM Nikos Balkanas <nbalka...@gmail.com> wrote: > Thx Marcus for the clarifications, > > On Mon, Apr 28, 2025 at 4:37 PM Marcus D. Leech <patchvonbr...@gmail.com> > wrote: > >> On 28/04/2025 05:33, Nikos Balkanas wrote: >> >> Compiled uhd 4.6.0 in debug mode. >> From the output I get: >> >> [DEBUG] [0/Radio#0] spp(= samples per package) value 2032 exceeds MTU of >> 8000! Coercing to 1996 >> Mon Apr 28 09:57:02 2025 [00] [*] scanner.l:1443:main Incorrect >> maxsamples (1996). Expected 19960. >> Mon Apr 28 09:57:02 2025 [00] [+] Max samples/buffer[0]: 1996 >> 1) Line mtu is 9000 not 8000 >> 2) 2032 is not larger than 8000 <= Bug? >> 3) seems that spp is setting my maxsmps >> >> That's number of *SAMPLES*. Samples are 4 bytes total. >> > > Aaaah. I'll have to check the SPB option. Otherwise an 80K MTU is > unreasonable:) > This also means that 1 sample = 1 real + 1 imag = 32 bits with sc16 > encoding > > . >> > > A lot of network hardware, particularly 1Gbit hardware doesn't *ACTUALLY* >> support an MTU of more than 8000, and I think >> UHD uses PMTU discovery. I found that with RealTek NICs, even when >> you set the MTU to 9000, it actually only supports >> 8000. >> >> Same case with my Mellanox NIC. But 8000 is close enough:) > >> >> >> Of the examples I tried the rx_samples_c. It is the same case like mine: >> single usrp. We use the same commands >> and we are getting the same output:( 1996 maxsmpls. >> The error text and code are from host/lib/rfnoc/radio_control_impl.cpp: >> 199 >> I would rather not touch it. I don't know the uhd architecture and >> especially the rfnoc/uhd interface. >> Besides I am a c programmer, not c++:( >> multi_usrp class has a set_rx_spp function, but it is not for me:( >> >> You can look at the benchmark_rate example to see how to set a >> samples-per-buffer other than the default, which is >> based on the MTU. It uses an "SPB" command-line parameter. >> >> Thx, I will check it out, when I get back to ubuntu.. Now I am in > windows:( > benchmark_rate uses the multi-usrp class. > >> >> HTH >> Nikos >> >> On Mon, Apr 28, 2025 at 6:02 AM Nikos Balkanas <nbalka...@gmail.com> >> wrote: >> >>> Point taken:) I'm proposing smt different: >>> pchar +ICMP are just to test line and connectors. First step. Not to >>> bench USRP. >>> benchmark_rate is to bench/stress usrp. >>> These 2 are independent, and complementary. >>> Pchar is telling me nothing more than my fiber cable and connectors are >>> good. >>> It saved me a trip tomorrow to my local PC store, where fiber cable and >>> connectors are ~7 E each. >>> benchmark_rate on the other hand is quite interesting. >>> It points to software,and particularly my uhd_init() >>> >>> Just found and downloaded the sources to uhd 4.6.0 from Ubuntu Launchpad. >>> Now I can go through the source of the example you told me:) >>> Ettus used to keep an archive of old uhd sources around. Seems it's >>> gone:( >>> Open source means, among others, free to choose the source version that >>> you need... >>> Having the latest source in Github is only partly open source. >>> During development we need to freeze updates. When in 5 years we go >>> into production we can't find the old sources anymore:( >>> If a customer discovers a bug, not in our code, but in one of the >>> libraries that >>> we use, what are we gonna do? >>> >>> BR >>> Nikos >>> >>> >>> >>> On Mon, Apr 28, 2025 at 5:01 AM Marcus D. Leech <patchvonbr...@gmail.com> >>> wrote: >>> >>>> On 27/04/2025 21:58, Nikos Balkanas wrote: >>>> >>>> My bad: >>>> >>>> throughput of 5.619 Kb/s requesting ICMP replies, +> throughput of >>>> 5,619 Kb/s requesting ICMP replies >>>> Local thousand separator is ".", whereas in the US is ",":( >>>> >>>> It is STILL the case that the ICMP machinery in these radios is >>>> ABSOLUTELY NOT on the fast-path inside >>>> the hardware. The only way to get a good feel for how much sample >>>> bandwidth they can process is >>>> with examples like "benchmark_rate". >>>> >>>> >>>> >>>> On Mon, Apr 28, 2025 at 12:37 AM Nikos Balkanas <nbalka...@gmail.com> >>>> wrote: >>>> >>>>> Hi Marcus, >>>>> >>>>> You were right. No need to change NIC:) >>>>> This is not a software issue. uhd_rx_streamer_max_num_samps runs right >>>>> after uhd initialization before >>>>> any other code had the chance to run. >>>>> Link capacity doesn't seem to be the issue either... >>>>> Running pchar on the link, descendant of pathchar, reports a >>>>> throughput of 5.619 Kb/s requesting ICMP replies, >>>>> to varying packet sizes (32->9000 (MTU), incr by 32). >>>>> sudo pchar -m 9000 -p ipv4icmp usrp >>>>> https://www.kitchenlab.org/www/bmah/Software/pchar/ >>>>> >>>>> It corresponds to 351.218.019 16-bit samples or 175,609.044 32-bit >>>>> samples, if each sample is 32-bit(real + imag) >>>>> Seems that uhd is not running at link capacity but is doing smt else. >>>>> I will have to download and check with the sources... >>>>> The package version for Ubuntu 24.04 is uhd 4.6.0. >>>>> Where can I download the sources for uhd 4.6.0? >>>>> >>>>> BR >>>>> Nikos >>>>> >>>>> On Sat, Apr 26, 2025 at 7:02 AM Nikos Balkanas <nbalka...@gmail.com> >>>>> wrote: >>>>> >>>>>> Thanks for your time. >>>>>> I will check out the example. >>>>>> This is not a buffer problem. I just need 1024 Samples >>>>>> (real+imaginary) for FFT... >>>>>> I should be able to get them in a single pass. >>>>>> You saw my code, not a smoking gun there. >>>>>> >>>>>> This is probably is a physical problem. >>>>>> Cable is an SFP fiber dedicated line. Cannot go bad. >>>>>> Maybe the connections are not sitting right :(... >>>>>> >>>>>> BR >>>>>> Nikos >>>>>> >>>>>> On Sat, Apr 26, 2025 at 6:45 AM Marcus D. Leech < >>>>>> patchvonbr...@gmail.com> wrote: >>>>>> >>>>>>> On 25/04/2025 23:33, Nikos Balkanas wrote: >>>>>>> >>>>>>> Actually MTU is 9000. This is one of the recommendations... >>>>>>> I tried it with MTU 1500. It was worse:( >>>>>>> maxsamples dropped to 364... >>>>>>> >>>>>>> Right, 9000, rather than 8000. >>>>>>> >>>>>>> Upgrading to 10Gbit wont' give you larger MTU. >>>>>>> >>>>>>> What you're trying to do, I think, is to solve a buffer-management >>>>>>> problem in your *application* at entirely the wrong >>>>>>> level in the stack. >>>>>>> >>>>>>> It is EXCEEDINGLY COMMON for hardware drivers to only be able to >>>>>>> deliver in chunks that may not be perfectly adapted to >>>>>>> the requirements of your application. So, a common programming >>>>>>> pattern is to deal with this in your application. >>>>>>> >>>>>>> You should probably look at example code like rx_samples_to_file >>>>>>> >>>>>>> >>>>>>> >>>>>>> [INFO] [UHD] linux; GNU C++ version 13.2.0; Boost_108300; >>>>>>> UHD_4.6.0.0+ds1-5.1ubuntu0.24.04.1 >>>>>>> [INFO] [X300] X300 initialization sequence... >>>>>>> [INFO] [X300] Maximum frame size: 1472 bytes. >>>>>>> [WARNING] [X300] For the 192.168.40.2 connection, UHD recommends a >>>>>>> send frame size of at least 8000 for best >>>>>>> performance, but your configuration will only allow 1472.This may >>>>>>> negatively impact your maximum achievable sample rate. >>>>>>> Check the MTU on the interface and/or the send_frame_size argument. >>>>>>> [WARNING] [X300] For the 192.168.40.2 connection, UHD recommends a >>>>>>> receive frame size of at least 8000 for best >>>>>>> performance, but your configuration will only allow 1472.This may >>>>>>> negatively impact your maximum achievable sample rate. >>>>>>> Check the MTU on the interface and/or the recv_frame_size argument. >>>>>>> [INFO] [GPS] No GPSDO found >>>>>>> [INFO] [X300] Radio 1x clock: 200 MHz >>>>>>> [WARNING] [UDP] The send buffer could not be resized sufficiently. >>>>>>> Target sock buff size: 24912805 bytes. >>>>>>> Actual sock buff size: 1048576 bytes. >>>>>>> See the transport application notes on buffer resizing. >>>>>>> Please run: sudo sysctl -w net.core.wmem_max=24912805 >>>>>>> Sat Apr 26 06:30:34 2025 [00] [+] Created USRP with args >>>>>>> Sat Apr 26 06:30:34 2025 [00] [+] Master clock is at 200 Mhz >>>>>>> Sat Apr 26 06:30:34 2025 [00] [+] Tuner[0] gain set to 30 (30) dB >>>>>>> [WARNING] [UDP] The send buffer could not be resized sufficiently. >>>>>>> Target sock buff size: 24912805 bytes. >>>>>>> Actual sock buff size: 1048576 bytes. >>>>>>> See the transport application notes on buffer resizing. >>>>>>> Please run: sudo sysctl -w net.core.wmem_max=24912805 >>>>>>> Sat Apr 26 06:30:34 2025 [00] [*] scanner.l:1446:main Incorrect >>>>>>> maxsamples (364). Expected 19960. >>>>>>> Sat Apr 26 06:30:34 2025 [00] [+] Max samples/buffer[0]: 364 >>>>>>> [WARNING] [0/Radio#0] Ignoring stream command for finite acquisition >>>>>>> of zero sam >>>>>>> >>>>>>> Nikos >>>>>>> >>>>>>> On Sat, Apr 26, 2025 at 5:46 AM Marcus D. Leech < >>>>>>> patchvonbr...@gmail.com> wrote: >>>>>>> >>>>>>>> On 25/04/2025 22:26, Nikos Balkanas wrote: >>>>>>>> >>>>>>>> Thanks Marcus, >>>>>>>> >>>>>>>> for your fast reply. >>>>>>>> >>>>>>>> On Sat, Apr 26, 2025 at 4:08 AM Marcus D. Leech < >>>>>>>> patchvonbr...@gmail.com> wrote: >>>>>>>> >>>>>>>>> On 25/04/2025 20:50, Nikos Balkanas wrote: >>>>>>>>> >>>>>>>>> Hello, >>>>>>>>> >>>>>>>>> I need to buy a new NIC. What would you suggest? >>>>>>>>> The one I use is an old Mellanox 10 Gbs, before the Connect-4 >>>>>>>>> series. >>>>>>>>> It can only do 1996 S/s, need 19960 (10x more) to work with latest >>>>>>>>> uhd. >>>>>>>>> Using Ubuntu 24.04 and uhd 4.6.0 >>>>>>>>> >>>>>>>>> So, 1.996ksps vs 19.960ksps? You hardly need a 10Gbit link to >>>>>>>>> support that. So, perhaps something >>>>>>>>> is being lost here in your requirements? >>>>>>>>> >>>>>>>> >>>>>>>> True. Can't explain it in terms of bandwidth. 16 * 1996 = 31.936 >>>>>>>> Kbps, 16 * 19960 = 319.360 Kbps well short of a 10 Gbps line:( >>>>>>>> Does a complex pair count as 1 sample, or 2? >>>>>>>> I have followed all the instructions in >>>>>>>> https://kb.ettus.com/USRP_Host_Performance_Tuning_Tips_and_Tricks, >>>>>>>> Even installed the DPDK drivers. My Mellanox is too old to use >>>>>>>> their OFED drivers:( >>>>>>>> >>>>>>>>> >>>>>>>>> On a related question. it seems that the streamer doesn't crash >>>>>>>>> anymore >>>>>>>>> when receiving less than MAXSPS samples, instead it reads 0:( >>>>>>>>> This was due to the sse2 code not aligned in convert. >>>>>>>>> I change my stream args to cpu_format=sc16, otw=sc16, so no >>>>>>>>> conversion required. >>>>>>>>> Streamer still doesn't read anything. Is there a reason for it? >>>>>>>>> >>>>>>>>> You'd need to share more of your code. This should just work as >>>>>>>>> far as I can tell. >>>>>>>>> >>>>>>>>> Thanks. these are just the usrp code: >>>>>>>> >>>>>>>> int main() >>>>>>>> { >>>>>>>> uhd_stream_args_t stream_args = >>>>>>>> { >>>>>>>> >>>>>>>> .cpu_format = "sc16", >>>>>>>> >>>>>>>> .otw_format = "sc16", >>>>>>>> .args >>>>>>>> = "", >>>>>>>> >>>>>>>> .n_channels = 1, >>>>>>>> >>>>>>>> .channel_list = &channel >>>>>>>> }; >>>>>>>> ..uhd_stream_cmd_t stream_cmd = >>>>>>>> { >>>>>>>> >>>>>>>> .stream_mode = UHD_STREAM_MODE_NUM_SAMPS_AND_DONE, >>>>>>>> >>>>>>>> .stream_now = true >>>>>>>> }; >>>>>>>> >>>>>>>> if (uhd_init(0, 0, gain)) do_exit(20); >>>>>>>>> if ((err = uhd_usrp_get_rx_stream(dev[0], &stream_args, >>>>>>>>> rx_streamer[0]))) >>>>>>>>> { >>>>>>>>> uhd_get_last_error(errmsg, 127); >>>>>>>>> error(log, "Failed to get streamer[0] (%d). %s.\n", 0, >>>>>>>>> FL, LN, FN, err, errmsg); >>>>>>>>> uhd_rx_streamer_free(&rx_streamer[0]); >>>>>>>>> rx_streamer[0] = NULL; >>>>>>>>> uhd_rx_metadata_free(&md[0]); >>>>>>>>> md[0] = NULL; >>>>>>>>> do_exit(30); >>>>>>>>> } >>>>>>>>> if ((err = uhd_rx_streamer_max_num_samps(rx_streamer[0], >>>>>>>>> &maxsamps))) >>>>>>>>> >>>>>>>> { >>>>>>>>> uhd_get_last_error(errmsg, 127); >>>>>>>>> error(log, "Failed to get max samples/buffer[0] (%d). >>>>>>>>> %s.\n", 0, FL, LN, FN, err, >>>>>>>>> ..errmsg); >>>>>>>>> do_exit(35); >>>>>>>>> } >>>>>>>>> if (maxsamps != MAXSMPS) >>>>>>>>> warn(log, "Incorrect maxsamples (%ld). Expected %d.\n", >>>>>>>>> 0, FL, LN, FN, maxsamps, >>>>>>>>> MAXSMPS); >>>>>>>>> info(log, "Max samples/buffer[0]: %ld\n", 0, maxsamps); >>>>>>>>> >>>>>>>>> if ((err = uhd_rx_streamer_issue_stream_cmd(rx_streamer[0], >>>>>>>>> &stream_cmd))) >>>>>>>>> >>>>>>>> { >>>>>>>>> uhd_get_last_error(errmsg, 127); >>>>>>>>> error(log, "Failed to start streamer[0] (%d). %s.\n", 0, >>>>>>>>> FL, LN, FN, err, errmsg); >>>>>>>>> do_exit(40); >>>>>>>>> } >>>>>>>>> >>>>>>>> [...] >>>>>>>> do_exit(0) >>>>>>>> } >>>>>>>> >>>>>>>> >>>>>>>>> bool uhd_init(size_t channel, double srate, double gain) >>>>>>>>> { >>>>>>>>> double tmp; >>>>>>>>> uhd_rx_metadata_error_code_t err; >>>>>>>>> >>>>>>>>> if ((err = >>>>>>>>> uhd_set_thread_priority(uhd_default_thread_priority, true))) >>>>>>>>> warn(log, "Unable to set main thread priority (%d). >>>>>>>>> %s.\n", 0, FL, LN, FN, >>>>>>>>> err, uhdError(err)); >>>>>>>>> /* Create USRP */ >>>>>>>>> f ((err = uhd_usrp_make(&dev[channel], "type=x300"))) >>>>>>>>> { >>>>>>>>> error(log, "Failed to create USRP (%d). %s.\n", 0, FL, >>>>>>>>> LN, FN, err, >>>>>>>>> uhdError(err)); >>>>>>>>> dev[channel] = NULL; >>>>>>>>> return(FAIL); >>>>>>>>> >>>>>>>> } >>>>>>>>> info(stderr, "Created USRP with args\n", 0); >>>>>>>>> >>>>>>>>> /* Create RX streamer */ >>>>>>>>> if ((err = uhd_rx_streamer_make(&rx_streamer[channel]))) >>>>>>>>> { >>>>>>>>> error(log, "Failed to create rx_streamer[%d] (%d). >>>>>>>>> %s.\n", 0, FL, LN, FN, >>>>>>>>> channel, err, uhdError(err)); >>>>>>>>> return(FAIL); >>>>>>>>> } >>>>>>>>> /* Create RX metadata */ >>>>>>>>> if ((err = uhd_rx_metadata_make(&md[channel]))) >>>>>>>>> { >>>>>>>>> error(log, "Failed to create md[%d] (%d). %s.\n", 0, FL, >>>>>>>>> LN, FN, channel, >>>>>>>>> err, uhdError(err)); >>>>>>>>> return(FAIL); >>>>>>>>> } >>>>>>>>> >>>>>>>>> /* Get master clock rate */ >>>>>>>>> if ((err = uhd_usrp_get_master_clock_rate(dev[channel], 0, >>>>>>>>> &tmp))) >>>>>>>>> >>>>>>>> { >>>>>>>>> error(log, "Failed to set master clock to %.0lf Mhz >>>>>>>>> (%d). %s.\n", 0, FL, >>>>>>>>> LN, FN, tmp/1000000, err, uhdError(err)); >>>>>>>>> return(FAIL); >>>>>>>>> } >>>>>>>>> info(stderr, "Master clock is at %.0lf Mhz\n", 0, >>>>>>>>> tmp/1000000); >>>>>>>>> /* Set the sample rate */ >>>>>>>>> if (srate && !uhd_set_rx_rate_check(channel, srate)) >>>>>>>>> return(FAIL); >>>>>>>>> /* Set the tuner gain SBX-120 is 0-31.5 in .5 db steps */ >>>>>>>>> >>>>>>>> if ((err = uhd_usrp_set_rx_gain(dev[channel], gain, >>>>>>>>> channel, ""))) >>>>>>>>> { >>>>>>>>> error(log, "Failed to set tuner[%d] gain to %.0lf db >>>>>>>>> (%d). %s.\n", 0, FL, >>>>>>>>> LN, FN, channel, gain, err, uhdError(err)); >>>>>>>>> return(FAIL); >>>>>>>>> } >>>>>>>>> if (!(err = uhd_usrp_get_rx_gain(dev[channel], channel, >>>>>>>>> "", &tmp))) >>>>>>>>> info(log, "Tuner[%d] gain set to %.0lf (%.0lf) >>>>>>>>> dB\n", 0, channel, tmp, gain); >>>>>>>>> >>>>>>>> ./* Set channel bw to conserve tuner resources. Not >>>>>>>> needed, set by srate */ >>>>>>>> uhd_usrp_set_rx_bandwidth(dev[channel], srate, >>>>>>>> channel); >>>>>>>> ./* Disable subtracting constant averaged background. >>>>>>>> Signal looks cleaner */ >>>>>>>> if ((err = >>>>>>>> uhd_usrp_set_rx_dc_offset_enabled(dev[channel], false, channel))) >>>>>>>> { >>>>>>>> warn(log, "Failed to disable FPGA DC offset on >>>>>>>> channel %d(%d). %s.\n", 0, >>>>>>>> FL, LN, FN, channel, err, uhdError(err)); >>>>>>>> } >>>>>>>> info(stderr, "Disabled FPGA DC offset on channel >>>>>>>> %d\n", 0, channel); >>>>>>>> return(SUCCESS); >>>>>>>> } >>>>>>>> >>>>>>>> This is the generated output: >>>>>>>> >>>>>>>> [INFO] [UHD] linux; GNU C++ version 13.2.0; Boost_108300; >>>>>>>> UHD_4.6.0.0+ds1-5.1ubuntu0.24.04.1 >>>>>>>> [INFO] [X300] X300 initialization sequence... >>>>>>>> [INFO] [X300] Maximum frame size: 8000 bytes. >>>>>>>> [INFO] [X300] Radio 1x clock: 200 MHz >>>>>>>> Sat Apr 26 03:33:48 2025 [00] [+] Created USRP with args >>>>>>>> Sat Apr 26 03:33:48 2025 [00] [+] Master clock is at 200 Mhz >>>>>>>> Sat Apr 26 03:33:48 2025 [00] [+] Tuner[0] gain set to 30 (30) dB >>>>>>>> Sat Apr 26 03:33:48 2025 [00] [*] scanner.l:1446:main Incorrect >>>>>>>> maxsamples (1996). Expected 19960. >>>>>>>> Sat Apr 26 03:33:48 2025 [00] [+] Max samples/buffer[0]: 1996 >>>>>>>> [WARNING] [0/Radio#0] Ignoring stream command for finite >>>>>>>> acquisition of zero samples >>>>>>>> I hope this reads OK. Maybe next time I should attach the code:) >>>>>>>> >>>>>>>>> TIA >>>>>>>>> Nikos >>>>>>>>> >>>>>>>>> _______________________________________________ >>>>>>>>> USRP-users mailing list -- usrp-users@lists.ettus.com >>>>>>>>> To unsubscribe send an email to usrp-users-le...@lists.ettus.com >>>>>>>>> >>>>>>>>> >>>>>>>>> I believe that max number of samples-per-buffer is limited by MTU >>>>>>>> size. Which is typically around 8000 or so for "jumbo frames". >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> >>>> >>
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