6 Jun
2006
6 Jun
'06
11:25 a.m.
I have a realtime audio/video system that almost works fine. I'm not
too terribly concered with latency, so I'm using 400 samples of
buffering both in and out. For the most part it all works. System load
is about 1.5 according to top, and the 3 processes of my system list
approximately 75% combined CPU usage.
However, I need the system to be network connected. I need it to have
sshd, snmpd, and some web server (not yet decided upon) running. When I
turn them on, any network traffic to either service causes glitches in
the audio, and possibly lost video frames.
I am using Linux 2.6.12 plus bigphysarea patch. I'm using a custom
non-Alsa sound card driver (when I started, I needed all of the AES
metadata, but I no longer do. At this point it is too late for me to
convert to using alsa though). I can provide my kernel .config file if
that would help.
I have CONFIG_PREEMPT and CONFIG_PREEMPT_BKL on. My application runs
with SCHED_FIFO and has an elevated priority, but not realtime
priority. When I tried setting it to realtime priority it grinds the
networking, control panel, and VGA display applications to a halt.
If I set the audio driver to loop back, the network never interupts it.
It would be difficult to move the entire audio portion of my system into
a kernel module though.
I've been watching for awhile and haven't seen to much about how to fix
this. Meanwhile, I've been tangling with this for months.
--
Joshua D. Boyd
jdboyd(a)jdboyd.net
http://www.jdboyd.net/
http://www.joshuaboyd.org/
6 Jun
6 Jun
1:39 p.m.
On Tue, 2006-06-06 at 11:10 -0400, Joshua Boyd wrote:
I have CONFIG_PREEMPT and CONFIG_PREEMPT_BKL on. My
application runs
with SCHED_FIFO and has an elevated priority, but not realtime
priority. When I tried setting it to realtime priority it grinds the
networking, control panel, and VGA display applications to a halt.
Uhhh, SCHED_FIFO and "realtime priority" are the same thing.
Can you be more specific?
Lee
2:46 p.m.
On Tue, Jun 06, 2006 at 01:39:31PM -0400, Lee Revell wrote:
On Tue, 2006-06-06 at 11:10 -0400, Joshua Boyd wrote:
setpriority(PRIO_PROCESS, 0, -20);
I was under the impression that that set priority to a "realtime"
priority, although rereading the man page I don't see any specific
correlation listed between -20 and realtime.
I also do: sched_setscheduler(0, SCHED_FIFO, &sp);
When I do the setpriority to -20, basically everything other than the
main application grinds to a halt. If I use -10 instead, other programs
work fine, but networking is then allowed to interfere with the main
program.
Is this specific enough?
I also should probably have mentioned that my application (actually
three programs on one box) is heavily threaded.
--
Joshua D. Boyd
jdboyd(a)jdboyd.net
http://www.jdboyd.net/
http://www.joshuaboyd.org/
I have CONFIG_PREEMPT and CONFIG_PREEMPT_BKL on.
My application runs
with SCHED_FIFO and has an elevated priority, but not realtime
priority. When I tried setting it to realtime priority it grinds the
networking, control panel, and VGA display applications to a halt.
Uhhh, SCHED_FIFO and "realtime priority" are the same thing.
Can you be more specific? 
3:06 p.m.
On Tue, 2006-06-06 at 14:31 -0400, Joshua Boyd wrote:
On Tue, Jun 06, 2006 at 01:39:31PM -0400, Lee Revell
wrote:
Just checking - is the SCHED_FIFO thread ever yielding the CPU? Or is it
just running a loop without ever sleeping or waiting for some lock?
--
Lars Luthman - please encrypt any email sent to me if possible
PGP key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x04C77E2E
Fingerprint: FCA7 C790 19B9 322D EB7A E1B3 4371 4650 04C7 7E2E
On Tue, 2006-06-06 at 11:10 -0400, Joshua Boyd
wrote:
setpriority(PRIO_PROCESS, 0, -20);
I was under the impression that that set priority to a "realtime"
priority, although rereading the man page I don't see any specific
correlation listed between -20 and realtime.
I also do: sched_setscheduler(0, SCHED_FIFO, &sp);
When I do the setpriority to -20, basically everything other than the
main application grinds to a halt. If I use -10 instead, other programs
work fine, but networking is then allowed to interfere with the main
program. I have CONFIG_PREEMPT and CONFIG_PREEMPT_BKL on.
My application runs
with SCHED_FIFO and has an elevated priority, but not realtime
priority. When I tried setting it to realtime priority it grinds the
networking, control panel, and VGA display applications to a halt.
Uhhh, SCHED_FIFO and "realtime priority" are the same thing.
Can you be more specific?
7:29 p.m.
On Tue, Jun 06, 2006 at 08:51:13PM +0200, Lars Luthman wrote:
On Tue, 2006-06-06 at 14:31 -0400, Joshua Boyd wrote:
Every thread in the process (since as I understand it, every thread in
the process is being set to sched_fifo) blocks on something. The video
thread blocks on the video card, the audio thread on the audio card, and
most other threads block on pthread_cond_waits (one house keeping thread
blocks on sleeps).
On Tue, Jun 06, 2006 at 01:39:31PM -0400, Lee
Revell wrote:
Just checking - is the SCHED_FIFO thread ever yielding the CPU? Or is it
just running a loop without ever sleeping or waiting for some lock? On Tue, 2006-06-06 at 11:10 -0400, Joshua Boyd
wrote:
setpriority(PRIO_PROCESS, 0, -20);
I was under the impression that that set priority to a "realtime"
priority, although rereading the man page I don't see any specific
correlation listed between -20 and realtime.
I also do: sched_setscheduler(0, SCHED_FIFO, &sp);
When I do the setpriority to -20, basically everything other than the
main application grinds to a halt. If I use -10 instead, other programs
work fine, but networking is then allowed to interfere with the main
program. I have CONFIG_PREEMPT and CONFIG_PREEMPT_BKL on.
My application runs
with SCHED_FIFO and has an elevated priority, but not realtime
priority. When I tried setting it to realtime priority it grinds the
networking, control panel, and VGA display applications to a halt.
Uhhh, SCHED_FIFO and "realtime priority" are the same thing.
Can you be more specific? 
7 Jun
7 Jun
8:53 a.m.
On Tue, 2006-06-06 at 14:31 -0400, Joshua Boyd wrote:
setpriority(PRIO_PROCESS, 0, -20);
I was under the impression that that set priority to a "realtime"
priority, although rereading the man page I don't see any specific
correlation listed between -20 and realtime.
there is no relationship whatsoever.
I also do: sched_setscheduler(0, SCHED_FIFO, &sp);
on POSIX-ish operating systems, there are two orthogonal aspects to
scheduling: scheduling class and scheduling priority. priority only
ranks different execution contexts (kernel threads) within the *same*
scheduling class - it has no impact when a scheduling decision has to be
made between two execution contexts in two different classes. put
differently, you can leave yourself in SCHED_OTHER (the default class)
and raise your priority to the maximum, but you will never ever be
scheduled to run if there is a SCHED_FIFO thread ready to run even if
its numerical priority is lower than yours.
there is no reason to use setpriority() for realtime work:
sched_setscheduler's parameter argument defines the priority.
--p
6:38 p.m.
On Wed, Jun 07, 2006 at 08:53:53AM -0400, Paul Davis wrote:
on POSIX-ish operating systems, there are two
orthogonal aspects to
scheduling: scheduling class and scheduling priority. priority only
ranks different execution contexts (kernel threads) within the *same*
scheduling class - it has no impact when a scheduling decision has to be
made between two execution contexts in two different classes. put
differently, you can leave yourself in SCHED_OTHER (the default class)
and raise your priority to the maximum, but you will never ever be
scheduled to run if there is a SCHED_FIFO thread ready to run even if
its numerical priority is lower than yours.
there is no reason to use setpriority() for realtime work:
sched_setscheduler's parameter argument defines the priority.
Well, my code is cleaner now at least then.
4:12 a.m.
On Tue, 06 Jun 2006 13:39:31 -0400
Lee Revell <rlrevell(a)joe-job.com> wrote:
On Tue, 2006-06-06 at 11:10 -0400, Joshua Boyd wrote:
Don't some people refer to the maximum static SCHED_FIFO prio as
"realtime priority". What was it again 99? or 100?
Flo
--
Palimm Palimm!
http://tapas.affenbande.org
I have CONFIG_PREEMPT and CONFIG_PREEMPT_BKL on.
My application runs
with SCHED_FIFO and has an elevated priority, but not realtime
priority. When I tried setting it to realtime priority it grinds the
networking, control panel, and VGA display applications to a halt.
Uhhh, SCHED_FIFO and "realtime priority" are the same thing.
Can you be more specific?
2:14 p.m.
On Wed, 2006-06-07 at 10:12 +0200, Florian Paul Schmidt wrote:
On Tue, 06 Jun 2006 13:39:31 -0400
Lee Revell <rlrevell(a)joe-job.com> wrote:
That's an incorrect useage, those people are wrong ;-)
On Tue, 2006-06-06 at 11:10 -0400, Joshua Boyd
wrote:
Don't some people refer to the maximum static SCHED_FIFO prio as
"realtime priority". I have CONFIG_PREEMPT and CONFIG_PREEMPT_BKL on.
My application runs
with SCHED_FIFO and has an elevated priority, but not realtime
priority. When I tried setting it to realtime priority it grinds the
networking, control panel, and VGA display applications to a halt.
Uhhh, SCHED_FIFO and "realtime priority" are the same thing.
Can you be more specific? What was it again 99? or 100?
99.
Lee
6539
days inactive
6540
days old
linux-audio-user@lists.linuxaudio.org
8 comments
5 participants
participants (5)
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Florian Paul Schmidt -
Joshua Boyd -
Lars Luthman -
Lee Revell -
Paul Davis