Re: [PATCH] improving O(1)-J9 in heavily threaded situations

Ingo Molnar
2002-02-06T10:40:04Z

On Wed, 6 Feb 2002, Jussi Laako wrote:

> > > > tasks? If yes then renice them to -11.
>
> I tried to renice many of the processes with different combinations
> and didn't make any difference.

> Here's top screens of two badly behaving load combinations:

> CPU states: 14.3% user, 11.9% system, 0.0% nice, 73.6% idle

73% of CPU time is idle! So priorities will make no (or little)
difference.

> PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND
> 809 root 15 0 58312 14M 3744 S 11.8 5.7 1:12 X
> 946 visitor 15 0 9572 9572 3584 S 8.0 3.7 0:26 guispect
> 999 visitor 15 0 1616 1616 1324 S 2.2 0.6 0:01 spectrum
> 944 visitor 15 0 1184 1184 984 S 1.5 0.4 0:03 soundsrv2
> 939 visitor 15 0 1184 1184 984 R 1.4 0.4 0:06 soundsrv2
> 1000 visitor 15 0 1236 1236 1024 S 0.7 0.4 0:00 streamdist
> 943 visitor 15 0 1236 1236 1024 S 0.5 0.4 0:02 streamdist
> 912 visitor 15 0 4564 4564 3544 R 0.2 1.7 0:00 gnome-terminal

since there is lots of idle CPU time left, the only thing that could make
a difference is timeslice length.

to 'fix' this (temporarily), renice all the non-SCHED_FIFO processes to
nice +19, that will give them the minimum timeslice length.

still dropped sound? If this fixes it then we can think about ways to fix
it for real.

again, what does it need to cause the 'bad' situation - too much latency
in the sound delivery path causing the audio buffers to starve? (or audio
buffers to be dropped?)

> CPU states: 19.4% user, 27.7% system, 0.0% nice, 52.7% idle

idle time in this snapshot too.

Ingo