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Re: [Discuss-gnuradio] b210 overflows and huge usb buffer

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] b210 overflows and huge usb buffer
Date: Sun, 11 Jan 2015 22:38:50 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0

On 01/11/2015 10:26 PM, Juha Vierinen wrote:

Now that the b210 timing issue now solved (thanks to Ian and Balint!), I'm trying to get samples to disk at about 50 MHz. I have more than the required bandwidth on the disk, but there are occasional I/O hiccups. With the N2x0 I just set the recv_buff_size to 1e9 and that solves pretty much all the I/O hangups I get. With the b210 there seems to be a driver imposed limit on the number of receive frames however, which prevent me from increasing num_recv_frames above 2000. At higher values, I get a uhd driver error and no samples come out of the uhd source. How can I increase the usb buffers on the b210 to about 1-2 GB? I don't care about latency, I just want to avoid long gaps in the data that are caused by the disk occasionally hanging up. I have tested the b210 with a null sink and there are no dropped packets.

I've tried everything to reduce disk hangups by changing the filesystem cache settings with some limited help, but I still can't completely remove occasional usb 3.0 packet drops. I'm convinced that simply using a multi gigabyte buffer is the easy way out solution, but I can't make this happen with the current uhd driver.


Those limits are likely not imposed by UHD, per se, but by underlying libusb implementation details, and the drivers in the kernel that "feed" libusb, and then
  the hardware USB controllers.

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