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Re: [Discuss-gnuradio] Expensive file write operation


From: sumit kumar
Subject: Re: [Discuss-gnuradio] Expensive file write operation
Date: Fri, 30 Aug 2019 19:56:57 +0200

Hi Nate, 
Ok I understood your point. Thanks for the Freq hint :) , I missed that in hurry.
Regards
Sumit 

On Fri, 30 Aug 2019 at 19:50, Nate Temple <address@hidden> wrote:
Hi Sumit,

The change for the output type doesn't address the limits of the transport. The output change however does cut the rate of data you're storing to disk in half, which can be useful if you have longer recordings or if your SSD is the bottle neck.

This Akitio adapter box paired with a Mellanox card is a setup we have tested for TB3 to 10Gb:

https://www.newegg.com/akitio-model-t3pb-t3dis-aktu/p/N82E16814988001
https://store.mellanox.com/products/mellanox-mcx4121a-acat-connectx-4-lx-en-network-interface-card-25gbe-dual-port-sfp28-pcie3-0-x8-rohs-r6.html

I have not personally used this QNAP product, but others have reported it works fine (you'd want the one with the SFP port)

https://www.qnap.com/en-us/product/qna-tb-10gbe


One other observation on your flowgraph, you do not have the Ch1 Center Freq set correctly, it is currently set as 0.


Regards,
Nate Temple


On Fri, Aug 30, 2019 at 10:42 AM sumit kumar <address@hidden> wrote:
Hi Nate, 
Thanks. 
My understanding about this was wrong :D I will order one adapter. 
Meanwhile, I tried your suggestion, it is still giving overruns. 
I have attached the screenshots of my config, can you please verify. 
Screenshot from 2019-08-30 19-37-03.png
Screenshot from 2019-08-30 19-37-16.png
Screenshot from 2019-08-30 19-37-49.png


On Fri, 30 Aug 2019 at 19:12, Nate Temple <address@hidden> wrote:
Hi Sumit,

Are you using a 1Gb transport to the X310?

The max data rate a 1Gb link can handle is ~25 MS/s @ sc16 OTW. With the two channels at 20 MS/s you're over this limit and would need to use 10Gb. If your laptop has a TB3/USB-C port, there are several TB3 to 10Gb adapters available.


Another observation -- if you switch the output type of the UHD Source block to be Complex int16 and then set your file sinks to have the data type Ints, you will cut the data rate in half that is being written to disk (complex 16bit Ints vs complex 32 bit floats).

Regards,
Nate Temple


On Fri, Aug 30, 2019 at 9:59 AM sumit kumar <address@hidden> wrote:
Hi, 
I am trying to capture RF data thru X310 from 2 channels and writing them to file using GNU Radio. But when I use a sampling rate of 20 MHz, packets start dropping badly. 

I have a very decent Laptop i7 8th Gen, SSD, 16 gb RAM. I also observed the CPU performance, it does not look stressed at all. I mean, none of the cores were reaching anywhere near to even 50%. 
Am I doing something wrong? For 10MHz sampling rate it is good, no overruns. 
I have attached my flowgraph, and the cpu performance screenshot. 


Screenshot from 2019-08-30 18-16-37.png
Screenshot from 2019-08-30 18-28-04.png
Screenshot from 2019-08-30 18-16-57.png

Regards
--
Sumit Kumar


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