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Re: [Discuss-gnuradio] New implementation for fusb_linux withoutallocs/f

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] New implementation for fusb_linux withoutallocs/frees
Date: Tue, 24 Feb 2009 10:03:05 -0500
User-agent: Thunderbird (X11/20090105)

Stefan Bruens wrote:
> Hi,
> attached is a new version for fusb_linux.cc.
> The current implementation uses three std::list lists for free, pending and 
> completed urbs, so submitting a single urb causes three allocs and three 
> frees 
> (pushing and popping of the list).
> The new implementation uses a circular list for the urbs, where each urb is 
> marked as free, pending or completed. As the total number of allocated urbs 
> is 
> constant, no allocs or frees are needed.
> Benchmark:
> usrp/host/apps/test_usrp_standard_tx -B 512 -N 64 -M 128
> old code needs ~990e6 instructions, new code 690e6 instructions. The call to 
> usrp_basic_tx::write goes down from 380e6 to 80e6 (so almost down to a fifth 
> ...), the remaining instructions is the pattern fill for the sample buffer.
> Regards,
> Stefan
Have you tested receive performance, and is it improved?

Bandwidth is my dearest friend in radio astronomy (in the absence of
RFI), so getting the best USB performance
  that's possible given CPU constraints is important to me.

Marcus Leech
Principal Investigator, Shirleys Bay Radio Astronomy Consortium

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