Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4]

[Florian Schmidt <mista.tapas@gmx.net>]

On Sun, 31 Oct 2004 16:59:13 +0100
Florian Schmidt <mista.tapas@gmx.net> wrote:

> p.s. new rtc_wakeup version uploaded, which shows the percentage converted
> to usecs (always positive, you need the sign?). btw: with V0.6.2 i sometimes
> see jitter > 100% but still no lost irq (/dev/rtc still reports only 1
> delivered irq on next wakeup). I cannot provke lost irqs with -f up to 2048.
> With -f 8192 i do get lost irq's [not amazing though].

another update upped. small bugfix (still depended on jack, should work now
w/o jack installed) plus minor cosmetic corrections. Here's example output
for 2.6.8.1-P9 (under heavy load (multiple finds plus kernel compile plus UI
artistics):

~/source/my_projects/rtc_wakeup$ ./rtc_wakeup 
rtc_wakeup - press ctrl-c to stop
freq:             1024
max # of irqs:    0 (run until stopped)
jitter threshold: 5% (48 usec)
output filename:  /dev/null
rt priority:      90(91)
getting cpu speed
1194913254.155 Hz (1194.913 MHz)
# of cycles for "perfect" period: 1166907 (976 usec)
setting up ringbuffer
setting up consumer thread
setting up /dev/rtc
locking memory
turning irq on, beginning measurement
new max. jitter: 1.6% (15 usec)
new max. jitter: 1.9% (18 usec)
new max. jitter: 2.6% (25 usec)
new max. jitter: 2.9% (28 usec)
new max. jitter: 3.2% (31 usec)
new max. jitter: 3.3% (31 usec)
new max. jitter: 3.3% (32 usec)
new max. jitter: 3.5% (34 usec)
new max. jitter: 3.5% (34 usec)
new max. jitter: 3.7% (35 usec)
new max. jitter: 4.3% (41 usec)
new max. jitter: 4.9% (47 usec)
threshold violated: 5.6% (54usec)
new max. jitter: 5.6% (54 usec)
threshold violated: 5.3% (51usec)
done.
total # of irqs:      168072
missed irqs:          0
threshold violations: 2
max jitter:           5.6% (54 usec)

So basically like lee said, 7% seems to be a normal upper limit for VP
boxes (there might be spikes though). 

V0.6.2 looked good, too, until it locked up again (under heavy load with
rtc_wakeup running) ;) Will build one with debugging enabled tomorrow. 

flo