[ardour-users] [Fwd: crash on loading session, - priority settings and latency]

Allan Klinbail allan_k at dodo.com.au
Thu Jan 6 12:12:22 PST 2005


Hi All 

This may be a developer issue but I'll start this here to see if anyone
else has come across this. 

After rebuilding my gentoo system with new Host optimisations
(--mfpmath=sse,387), which also included moving up to ardour 0.9_beta22.
I tried some load testing. I was using 8 stereo tracks, I found I could
load 4 complex plugins per stereo channel up to the 5th channel where my
DSP usage was reading around 90%. 

After pressing play the DSP usage actually dropped to around 60% and
stayed there after pressing stop for a short time then the CPU load
increased back up again... this is strange behaviour I believe.

I then added in some more plugins and built it up again.  When I tried
to reload the session after closing and starting again ardour crashed
each and every time, disconnecting from Jack but also freezing. I ahve
seen this behaviour before with MusE, so applied the same methodology to
ardour. 

After finding the PID's of ardour I issued a schedtool command to see
what scheduling systems were used and their priority settings. Here is
the result 

PID 16946: PRIO   0, POLICY N: SCHED_NORMAL, AFFINITY 0x1
PID 16947: PRIO  10, POLICY F: SCHED_FIFO  , AFFINITY 0x1
PID 16948: PRIO   0, POLICY N: SCHED_NORMAL, AFFINITY 0x1
PID 16952: PRIO   0, POLICY N: SCHED_NORMAL, AFFINITY 0x1
PID 16953: PRIO   9, POLICY F: SCHED_FIFO  , AFFINITY 0x1

As suspected the sched_fifo processes, looked to be a bit low.
Increasing the priority (using schedtool -F -p 50 16953 and again on
16947)   I found that ardour would not crash on loading the session. 

Unfortunately though while this resolved one issue, I found that I was
getting more xruns at this level. 

If anyone else has noticed this please let me know, especially if you
have found an optimal priority setting. Otherwise I guess this is help
for people who have the same issue. 

cheers 

-- 
Allan Klinbail <sonofzev at dodo.com.au>
-- 
Allan Klinbail <allan_k at dodo.com.au>





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