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Re: [Discuss-gnuradio] New implementation for fusb_linux without allocs/

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] New implementation for fusb_linux without allocs/frees
Date: Mon, 23 Feb 2009 07:05:07 -0800
User-agent: Mutt/1.5.18 (2008-05-17)

On Mon, Feb 23, 2009 at 07:38:14AM +0100, 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


Stefan, please tell me again how you measured the instruction count?

Also, if you haven't already, please send in the form that starts the
copyright assignment.  Contact me off-list if you've got any more
questions about that.


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