Xorg vs gettimeofday() and clock_gettime()

[John E Hein]

Peter Jeremy wrote at 21:07 +1100 on Feb 26, 2008:
 > My guess is pointer acceleration and/or 3-button emulation.  Out of
 > interest, I just ktrace'd my X server for 5 seconds (doing nothing in
 > particular) and got 318 syscalls, including 106 gettimeofday() calls.
 > By waving the mouse around inside a window, I get 4015 syscalls,
 > including 844 gettimeofday() and 1136 sigprocmask() calls in 5
 > secinds.  In some cases, there are consecutive gettimeofday() calls
 > with no other syscalls intervening.  These numbers do seem somewhat
 > excessive.

Interesting.  

I tried a ktrace session for about 10 seconds _without_ moving the
mouse and got 71332 gettimeofday calls out of 142707 total calls and
signals (all SIGALRM - 2051).

After about 7 minutes with mouse movement (and typing this message), I
saw 193356 gettimeofdays vs 502875 total.

I (obviously) haven't looked at the code.  But perhaps this is an area
that could possibly be improved by more judicious use of select or
kqueue and more independence of interval timing.