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Re: [Discuss-gnuradio] Re: UHD Announcement - February 25rd 2011


From: Josh Blum
Subject: Re: [Discuss-gnuradio] Re: UHD Announcement - February 25rd 2011
Date: Sun, 27 Feb 2011 19:16:39 -0800
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101208 Lightning/1.0b2 Thunderbird/3.1.7

> When you say "2x" performance increase, do you mean CPU performance or
> send()/recv() latency?  Do you mind saying a few words on what changes
> you have made?
> 

Much of the performance gains involved removing things out of the
fast-path that only needed to be called once at initialization (forgoing
code simplicity for performance). Example: a vector of pointers, a bound
callable object; many of which had calls to malloc and free which incurs
quite a lot of unnecessary overhead.

Less cpu cycles/less time are spent in the send()/recv() calls. This
roughly worked out to about half the CPU usage when looking at oprofile.
Because of this, the overall latency is reduced. We measured about 250us
RTT from device to host and back to device with the latency measurement
app in uhd examples.

-josh



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