Have you looked at the rtirq stuff to improve the performance of 3.x kernels?
On Sat, Nov 26, 2011 at 7:18 PM, Aere Greenway <a...@dvorak-keyboards.com>wrote: > ** > Ubuntu Studio Users: > > I think your plan to move Ubuntu Studio to Xubuntu is a good one. It > seems to have the lowest overhead of any of the Ubuntu versions. > > But it seems there are problems with the kernel itself, which even the > lower overhead of Xubuntu cannot solve. > > I have been working with the Fluidsynth developers to address another > problem, and in doing so, discovered the performance problem the testing > below attempts to quantify. > > > All: > > Your suggestion of cutting the sample rate did not seem to have any affect > that was visible to me. > > It may be that I would need to run without Jack, but I need Jack because I > use audio files. > > In the past, I have run without Jack, and the performance of Qsynth was > better, but not much better. I could test this further, but it is a moot > point, since I need to be able to use audio files in my sequences. > > I performed some benchmark testing on the problems I have been reporting. > > I did all of the following on a 933 megahertz unit-processor (one CPU) > machine, which has been my minimum system in my test-bed. > > I tried it on Ubuntu 11.04, and on Xubuntu 11.10. > > My methodology was to reduce the Qsynth polyphony parameter to the point > where my test sequence (MIDI) file yielded no underruns. I did a binary > search for the polyphony value that worked. I did not use Reverb, or > Chorus (the check-boxes were clear) in any of the tests. > > With polyphony values above 16, changes of 1 (up or down) made an > observable difference. > > I also noted (while the piece was playing) the Digital Signal Processing > load (shown in the Qjackctl window as Real Time Percentage (RT %). > > When I got down to the minimum Qsynth polyphony value of 16, I started > muting tracks, to where the maximum # of single-note-playing-at-a-time > tracks played with no under-runs. > > *UBUNTU 11.04* > > > Polyphony parameter value without under-runs: *26* > > DSP Load while playing: Usually in 20% range, sometimes in 30% range, > max 38.9% > > > *XUBUNTU 11.10* > > Polyphony paramater value without under-runs: *3* (16, with only 3 > tracks playing!) > > DSP Load while playing: In the 50% range, often getting up into the 60% > range. > > *Note: It will not play a single-track piano part without generating > under-runs. > > From past experience, I observed that UBUNTU 11.10 has a poorer > performance than XUBUNTU 11.10. Also, the Unity desktop appears to have > DSP Load values 20% higher than the cripple-ware Ubuntu Classic desktop on > the same machine. > > As you can see, the performance of the two systems is radically different > - an order of magnitude. It is not just a minor difference. > > The performance hit seems to be associated with the new kernel - not so > much the desktop. Though Kubuntu had the poorest performance of the three > I tried. > > A 2.5 gigahertz unit-processor system (using the Ubuntu Classic desktop) > will run the test piece without under-runs. > > I have a 1.5 gigahertz machine which I have not yet tried, but based on > the above, it will perform poorly, or perhaps marginally. > > On 11.04, all of these machines would perform the test piece on Qsynth > without under-runs (though on the 933 megahertz machine, the Qsynth > polyphony had to be set down to 26). > > I will do further testing with my 1.5 gigahertz machine, since this is one > of the target machines I originally planned to use. > > -- > > Sincerely, > Aere > > > -- > Ubuntu-Studio-users mailing list > Ubuntu-Studio-users@lists.ubuntu.com > Modify settings or unsubscribe at: > https://lists.ubuntu.com/mailman/listinfo/ubuntu-studio-users > >
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