On Tue, Aug 10, 2021 at 10:37 AM Marcus D. Leech <[email protected]>
wrote:

> On 08/10/2021 12:01 AM, Brian Padalino wrote:
>
> On Mon, Aug 9, 2021 at 2:12 PM Jonathan Tobin <[email protected]>
> wrote:
>
>> Just as an additional update - I was able to test with UHD 4.1 and there
>> is no issue - seems to be something with UHD 3.15 then.
>>
>
> Just chiming in here to ensure you understand that your test of receiving
> 625M samples using that particular program will keep all those samples in
> memory for all the channels while you receive.
>
> In other words, 10GB of RAM (625M samples * 4 bytes/sample/channel * 4
> channels) will be used just to hold your received signal.
>
> Brian:
>
> I don't think that's actually true.  The data are buffered in chunks of
> 'samps_per_buff' -- so there's only that much being stored at any given
>   time (at least in rx_multi_samples.cpp).
>

You're right - I should have consulted the code instead of make assumptions
when seeing some numbers printed out.

It follows as such from master:

The stream command num_samps is assigned the total number of samples here:


https://github.com/EttusResearch/uhd/blob/a7486cbfba959d7f55a9343db66eabee94786b2f/host/examples/rx_multi_samples.cpp#L136

... and the warning is actually printed out when issue_stream_cmd() is
called:


https://github.com/EttusResearch/uhd/blob/a7486cbfba959d7f55a9343db66eabee94786b2f/host/lib/rfnoc/radio_control_impl.cpp#L897

... and not when trying to actually recv().

Sorry for the misunderstanding.

Brian
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