compiz team mailing list archive

[Phil Doroff <764330@xxxxxxxxxxxxxxxxxx>]

I've successfully narrowed down the cause of this, and found a
workaround - for my systems.  I'm unsure if this will fix things for
anyone else, however.  I did find some items surprising here, and they
may warrant a deeper look.

This all came down to USB HID mouse sampling rates.  The logitech
reports a bInterval of 1, which is 1000Mhz.  For whatever reason (this
is likely a bug, I would imagine?) compiz appears to be doing work on
every mouse poll.  1000 times/sec = you get stuttering going on.  At
least in my case.

I also noticed throughout this that my Nvidia card was on APIC
interrupts - while this did not end up being the root cause, it's
certainly not good.  Check that out as well perhaps, fix is:

options nvidia-current NVreg_EnableMSI=1 in /etc/modprobe.d/nvidia.conf

For now, my workaround on the performance issue is to simply limit mouse
polling to something sane.  This is done by creating a file (anything
will do really) in /etc/modprobe.d/usbhid.conf

Add: 
options usbhid mousepoll=10 

- this is 125mhz, next up is 8, 6, 4, 2, and so on.  Go with the lowest
you enjoy - honestly I'm fine personally with 10 or 8.

I do wonder how many laptops (as reported here) utilize USB-based
trackpads?  I would imagine this would contribute to quite a bit of
battery drain in some use cases.  Good howto is here for further
reading: http://wiki.quakeworld.nu/Howto_customise_mouse_polling_rate

I can't imagine there is much benefit to compiz attempting to render
frames (or otherwise "do stuff") faster than a certain fail-safe.  At
least there should be a configured maximum somewhere - as I don't think
1000 frames/second is truly needed for my desktop window redraws :)  I
would imagine this bug exhibits itself more on nvidia hardware, due to
needing vsync turned off as well, but that's rampant speculation.

Hopefully this helps someone out there!

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https://bugs.launchpad.net/bugs/764330

Title:
  Move window annoying slow with compiz

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