Your add_blk27 usage seems high. This leads me to believe you may not have run volk_profile.

Run volk_profile in terminal. Since it's measuring timing, preferably without other processes interfering (for example, you should shut down stuff like web browsers and e-mail clients).

You could also use a lower final sample rate. You could pack your FM carriers every 400 kHz, and get away with a sampling rate around 2.4 Msps for five carriers. You could also try 200 kHz spacing, but your FM receiver may not like that.

Ron

On 10/14/20 18:07, Anish Mangal wrote:
That is what it seems like...
https://pasteboard.co/JvGuqC7.png

This is on i7-4900MQ. I also updated the gnuradio-companion to 3.8.2.0 (Python 3.6.9).



On Thu, Oct 15, 2020 at 1:33 AM Ron Economos <w...@comcast.net <mailto:w...@comcast.net>> wrote:

    The Rational Resampler uses a lot of CPU cycles. Upgrading to GNU
    Radio 3.8 won't help.

    Ron

    On 10/14/20 08:01, Anish Mangal wrote:
    Thanks. I'll look at both those points before reverting. :)

    On Wed, Oct 14, 2020 at 7:18 PM Marcus Müller <muel...@kit.edu
    <mailto:muel...@kit.edu>> wrote:

        again,

        1. outdated GNU Radio. More modern GNU Radio might perform
        better.
        Updating isn't really optional when you're musing about
        performance.
        2. actually benchmark where your CPU is going. `htop` is a
        good tool if
        you turn on "thread names" in its settings.

        Best regards,
        Marcus

        On 14/10/2020 15.26, Anish Mangal wrote:
        > Hi Marcus,
        >
        > Thanks for the quick reply. Here's a more complete flow
        diagram that
        > doesn't use the block I mentioned above.
        >
        > https://pasteboard.co/JvBTisO.png
        >
        > This uses up most of my CPU, so I was wondering whether it
        was possible
        > to spread this across multiple distinct computers. I'm
        sorry, that I
        > can't share my most up to date block diagram which uses
        actual audio
        > sources instead of coldplay songs, as it is on another
        machine which I
        > dont have access to at the moment, but this gives a fairly
        good idea
        > about the number of blocks and processing units.
        >
        > Thoughts?
        >
        >
        >
        > On Wed, Oct 14, 2020 at 6:48 PM Marcus Müller
        <muel...@kit.edu <mailto:muel...@kit.edu>
        > <mailto:muel...@kit.edu <mailto:muel...@kit.edu>>> wrote:
        >
        >     Hi Anish,
        >
        >     what your subject line says, distributing across CPUs,
        GNU Radio does
        >     automatically.
        >
        >     Across multiple distinct computers, you'll need to add
        some signal
        >     communications between these computers. The ZeroMQ
        network sinks and
        >     sources do that for you.
        >
        >     But honestly, the flow graph you show should use nearly
        no CPU at all.
        >     You should investigate what, in your overall flow
        graph, not just in
        >     the
        >     excerpt you showed, uses up your CPU. This should
        really not be a big
        >     task for your computer.
        >
        >     Also, you're using an outdated version of GNU Radio.
        Time to update!
        >
        >     Best regards,
        >     Marcus
        >
        >     On 14/10/2020 15.07, Anish Mangal wrote:
        >      > Hi, This is my very first post to this mailing list,
        so hello to
        >     all. I
        >      > am a beginner in experimenting with gnuradio and sdr
        >     (hackrf-one). I am
        >      > working on an application where I want to take
        multiple audio input
        >      > sources and transmit multiple FM signals over one RF
        channel via the
        >      > SDR. To this end, I created a basic grc block that
        looks like this:
        >      >
        >      > https://pasteboard.co/JvBGgj5.png
        >      >
        >      > My plan is to have a top level flow diagram using
        multiple such
        >     blocks
        >      > and sum them to produce a composite FM signal
        through the
        >     hackrf-one.
        >      > With my 4th generation intel i7 CPU, with the
        hackrf's bandwidth
        >     set to
        >      > 6MSPS, I am able to transmit 6 simultaneous fm
        modulated signals. My
        >      > question is this:
        >      >
        >      > Is it possible to spread this task across multiple
        computers. If one
        >      > computer could produce the FM modulated signals, and
        the other
        >     computer
        >      > sum them and transmit via the SDR, the number of
        simultaneous
        >     streams
        >      > may be increased.
        >      >
        >      > Another approach might be to offload parts of this
        block diagram
        >     to an
        >      > FPGA processing unit.
        >      >
        >      > My challenge is this. I have no experience of
        working with an
        >     FPGA, and
        >      > limited experience with gnu-radio in general, but I
        am prepared
        >     to put
        >      > in the effort required, however, if someone more
        experienced than
        >     me can
        >      > guide me on the proper approach to go about this, it
        would be very
        >      > helpful. It may be that I just keep all the
        processing on ONE
        >     powerful
        >      > CPU, and whatever is the max number of simultaneous
        streams I can
        >     get,
        >      > that's it. But if there are cost effective ways of
        making this
        >     design
        >      > more efficient, I'm happy to research and experiment.
        >      >
        >      > 73,
        >      > VU2TVE // Anish
        >      >
        >

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