CPU intensive touch-pad on the OpenMoko

Andy Green andy at openmoko.com
Wed Nov 5 01:48:24 CET 2008

Hash: SHA1

Somebody in the thread at some point said:
| Hi,
| it seems that using the touchpad causes alot of cpu usage. I have an
| application
| which reports mouse movement events to a function. So I have this area
| where I can press and drag around the pointer with the stylus.
Whenever I do
| that the CPU %sy utilization in top goes up to 50%-60%.. Shouldn't we be
| able to expect that we get more time for userspace than for the kernel
| if we just move the pointer around? 50-60% seems extremely absurd...
| PS if you want to test what I mean, download and install my application
| from:
| http://www.733kru.org/~pltxtra/OpenMoko/

I think this might be jumping to conclusions as to where the time in the
kernel is spent.  For example, run top alone without your app to find
the background use of /sys, then start using the touchscreen (still with
no app) while top runs and note the difference.  This would represent
the time taken by kernel to deal with touchscreen without any additional
time in kernel about something else caused by your app.  If it's still
50%, then we have a problem alright :-)

- -Andy
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