Alsa dmix high cpu usage

mrfomt

New Member
Have an Odroid Xu4 running Ubuntu 16.04 with retropie.
I had some problems with the pulseaudio, random distortions in the sound, tried to change configs and google about it a lot, but nothing that I found helps. So I decided to skip pulseaudio and only use Alsa with Dmix, and the sound works great! No problem at all with the sound. Added ”autospawn = no” to /etc/pulse/client.conf, but I notice some higher cpu usage. I have set sample rate with Alsa to 44100.
mpg123 uses 30%, and mplayer 80%.
With pulseaudio mpg123 it is 1-2% and mplayer 20-30%. Checked with command top.
I’m no expert at this, I have googled and tried to set it up correct, sound is working, but dont know why it uses more cpu.
I added softvol to asound.conf also, because in emulationstation I got an
VolumeControl::init() - Failed to find mixer elements!
But that dissapeard when adding softvol to asound.conf

Code:
$ cat /proc/asound/card0/pcm0p/sub0/hw_paramsaccess:
MMAP_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2
rate: 44100 (44100/1)
period_size: 1024
buffer_size: 4096
Here are the configs I have changed:


asound.conf

Code:
$ cat /etc/asound.conf

pcm.!default {

    type plug

    slave.pcm "softvol"

}

pcm.softvol {

      type softvol

      slave.pcm "dmixer"

      control {

          name "Master"

          card 0

      }

}

pcm.dmixer {

      type dmix

      ipc_key 1024



      slave {

        pcm "hw:0,0"

        period_time 0

        period_size 1024

        buffer_size 4096

        buffer_time 0

        channels 2

        rate 44100

}

      bindings {

          0 0

          1 1

      }

}





ctl.!default {

    type hw

    card 0

}

ctl.softvol {

    type hw

    card 0

}

ctl.dmixer {

    type hw

    card 0

}

/etc/pulse/default.pa

Code:
cat /etc/pulse/default.pa

#!/usr/bin/pulseaudio -nF

#

# This file is part of PulseAudio.

#

# PulseAudio is free software; you can redistribute it and/or modify it

# under the terms of the GNU Lesser General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# PulseAudio is distributed in the hope that it will be useful, but

# WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

# General Public License for more details.

#

# You should have received a copy of the GNU Lesser General Public License

# along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.



# This startup script is used only if PulseAudio is started per-user

# (i.e. not in system mode)



.nofail



### Load something into the sample cache

#load-sample-lazy x11-bell /usr/share/sounds/freedesktop/stereo/bell.oga

#load-sample-lazy pulse-hotplug /usr/share/sounds/freedesktop/stereo/device-added.oga

#load-sample-lazy pulse-coldplug /usr/share/sounds/freedesktop/stereo/device-added.oga

#load-sample-lazy pulse-access /usr/share/sounds/freedesktop/stereo/message.oga



.fail



### Automatically restore the volume of streams and devices

load-module module-device-restore

load-module module-stream-restore

load-module module-card-restore



### Automatically augment property information from .desktop files

### stored in /usr/share/application

load-module module-augment-properties



### Should be after module-*-restore but before module-*-detect

load-module module-switch-on-port-available



### Load audio drivers statically

### (it's probably better to not load these drivers manually, but instead

### use module-udev-detect -- see below -- for doing this automatically)

load-module module-alsa-sink device=dmix

load-module module-alsa-source device=hw:0,0

#load-module module-oss device="/dev/dsp" sink_name=output source_name=input

#load-module module-oss-mmap device="/dev/dsp" sink_name=output source_name=input

#load-module module-null-sink

#load-module module-pipe-sink



### Automatically load driver modules depending on the hardware available

.ifexists module-udev-detect.so

#load-module module-udev-detect tsched=0

.else

### Use the static hardware detection module (for systems that lack udev support)

#load-module module-detect 

.endif



### Automatically connect sink and source if JACK server is present

.ifexists module-jackdbus-detect.so

.nofail

load-module module-jackdbus-detect channels=2

.fail

.endif



### Automatically load driver modules for Bluetooth hardware

.ifexists module-bluetooth-policy.so

load-module module-bluetooth-policy

.endif



.ifexists module-bluetooth-discover.so

load-module module-bluetooth-discover

.endif



### Load several protocols

.ifexists module-esound-protocol-unix.so

load-module module-esound-protocol-unix

.endif

load-module module-native-protocol-unix



### Network access (may be configured with paprefs, so leave this commented

### here if you plan to use paprefs)

#load-module module-esound-protocol-tcp

#load-module module-native-protocol-tcp

#load-module module-zeroconf-publish



### Load the RTP receiver module (also configured via paprefs, see above)

#load-module module-rtp-recv



### Load the RTP sender module (also configured via paprefs, see above)

#load-module module-null-sink sink_name=rtp format=s16be channels=2 rate=44100 sink_properties="device.description='RTP Multicast Sink'"

#load-module module-rtp-send source=rtp.monitor



### Load additional modules from GConf settings. This can be configured with the paprefs tool.

### Please keep in mind that the modules configured by paprefs might conflict with manually

### loaded modules.

.ifexists module-gconf.so

.nofail

load-module module-gconf

.fail

.endif



### Automatically restore the default sink/source when changed by the user

### during runtime

### NOTE: This should be loaded as early as possible so that subsequent modules

### that look up the default sink/source get the right value

load-module module-default-device-restore



### Automatically move streams to the default sink if the sink they are

### connected to dies, similar for sources

load-module module-rescue-streams



### Make sure we always have a sink around, even if it is a null sink.

load-module module-always-sink



### Honour intended role device property

load-module module-intended-roles



### Automatically suspend sinks/sources that become idle for too long

load-module module-suspend-on-idle



### If autoexit on idle is enabled we want to make sure we only quit

### when no local session needs us anymore.

.ifexists module-console-kit.so

load-module module-console-kit

.endif

.ifexists module-systemd-login.so

load-module module-systemd-login

.endif



### Enable positioned event sounds

load-module module-position-event-sounds



### Cork music/video streams when a phone stream is active

#load-module module-role-cork



### Modules to allow autoloading of filters (such as echo cancellation)

### on demand. module-filter-heuristics tries to determine what filters

### make sense, and module-filter-apply does the heavy-lifting of

### loading modules and rerouting streams.

load-module module-filter-heuristics

load-module module-filter-apply



# X11 modules should not be started from default.pa so that one daemon

# can be shared by multiple sessions.



### Load X11 bell module

#load-module module-x11-bell sample=x11-bell



### Register ourselves in the X11 session manager

#load-module module-x11-xsmp



### Publish connection data in the X11 root window

#.ifexists module-x11-publish.so

#.nofail

#load-module module-x11-publish

#.fail

#.endif



### Make some devices default

#set-default-sink output

#set-default-source input
 


wizardfromoz

Super Moderator
Staff member
Gold Supporter
I’m no expert at this
Nor I ... but welcome to linux.org :)

Out of interest, did you try the two commands (pulseaudio) listed in @rado84 's Thread stickied to the top of the Audio-Video page?

Chris Turner
wizardfromoz
 

mrfomt

New Member
Nor I ... but welcome to linux.org :)
Thank you! :)

Out of interest, did you try the two commands (pulseaudio) listed in @rado84 's Thread stickied to the top of the Audio-Video page?
Yes I tried that, but it only fix it temporary,, disortion comes back again. But without pulseaudio I got no distortion at all, but I get much higher cpu usage with just alsa with dmix config, is that normal?
 

mrfomt

New Member
The xu4 has an Samsung Exynos5 Octa ARM Cortex-A15 Quad
So if it has 8 cores then the cpu usage I see in top-command should be divided in 8? So maybe isnt so high cpu usage?
But still much more than before..
 

rado84

Active Member
much higher cpu usage with just alsa with dmix config, is that normal?
I think the reason for the high CPU usage is that dmix thing. IDK what that is nor I never needed to know. I'm using ALSA too and never had a problem with it. Even now the CPU temperature is 28 degrees which means it's in the lower levels of its usage running at about 0.78 GHz (max is 3.70 GHz).
Try installing the package libasound2-plugins-extra. Then completely uninstall that dmix thing and see how your CPU behaves. Altough I wouldn't count much on performance bc this is an ARM CPU which in fact has nothing advanced in it. It's possible that ALSA wasn't optimized for ARM but I can't say that for sure cuz I'm not its developer.
 

JulienCC

Member
There's a chance that a part of alsa sound treatment happens in userland. So if any alsa plugin (such as softvol or dmix) takes some CPU power (which they do) it will impact the process that uses alsa (your players). Dmix and Softvol are software plugins. They have to recompute audio frames to combine them and to change the volume. These operations take CPU power. There's a high chance that these operations are floating point operations which are CPU intensive.

I you wish to reclaim these CPU% you should try to perform mixing and volume control in hardware.
 

Members online

No members online now.

Top