On 01/12/2015 12:17 PM, Juha Vierinen wrote:
I managed to find a solution to this. I create a ram filesystem
(tmpfs) and dump fixed length files there with gnuradio. I then move
the files when they are complete to a persistent drive using another
script. I don't know why I didn't think of this before.
juha
One of the issues with USB (of any flavour) is that it wasn't designed
with bulk performance in mind, really, so you have to kind of stand on your
head to get it.
Near as I can tell, in the USB driver world (at least on Linux), the
driver (via libusb) doesn't buffer the same way that is done in the
networking-stack.
There's no way to configure a seriously-huge buffer for traffic
that's in-flight.
On Mon, Jan 12, 2015 at 11:30 AM, Jeff Long <willco...@gmail.com
<mailto:willco...@gmail.com>> wrote:
On 01/11/2015 10:38 PM, Marcus D. Leech wrote:
On 01/11/2015 10:26 PM, Juha Vierinen wrote:
Hi,
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
I've streamed through programs like mbuffer before, to iron out an
uneven disk recording rate. But I can't say I understand all of
the GR and Linux buffering interaction well enough to be sure why
it worked.
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.
juha
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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