Liquidsoap Memory and CPU Performance: jemalloc vs. Default Allocator

[vitoyucepi]

Introduction

Liquidsoap can run with or without jemalloc, a memory allocator that aims to improve memory efficiency. If you have been using Liquidsoap with jemalloc and are now wondering if turning it off makes sense, I tested both setups to compare memory and CPU usage.

Setup

For this test, I utilized a Liquidsoap script that encodes MP3, OGG, and Opus audio streams from a single input source. The stream rotates through about 50 playlists, without using crossfade or compression. I ran the setup continuously for 6 days, once with the default memory allocator and once with jemalloc. I tracked:

• Memory usage;
• CPU usage.

Build config

 * Liquidsoap version  : 2.2.5

 * Compilation options
   - Release build       : true
   - Git SHA             : (none)
   - OCaml version       : 4.14.2
   - OS type             : Unix
   - Libs versions       : angstrom=0.16.1 asetmap=0.8.1 astring=0.8.5 base64=3.5.1 bigarray=[distributed with Ocaml] bigarray-compat=1.1.0 bigstringaf=0.10.0 bytes=[distributed with OCaml 4.02 or above] camlp-streams camomile.lib=2.0 cohttp=5.3.1 cohttp-lwt=5.3.0 cohttp-lwt-unix=5.3.0 conduit=7.1.0 conduit-lwt=7.1.0 conduit-lwt-unix=7.1.0 cry=1.0.3 ctypes=0.23.0 ctypes.stubs=0.23.0 curl=0.9.2 domain-name=0.4.0 dtools=0.4.5 dune-build-info=3.16.0 dune-private-libs.dune-section=3.16.0 dune-site=3.16.0 dune-site.private=3.16.0 duppy=0.9.4 ffmpeg-av=1.1.11 ffmpeg-avcodec=1.1.11 ffmpeg-avdevice=1.1.11 ffmpeg-avfilter=1.1.11 ffmpeg-avutil=1.1.11 ffmpeg-swresample=1.1.11 ffmpeg-swscale=1.1.11 fileutils=0.6.4 fmt=0.9.0 gen=1.1 inotify=v2.6 integers ipaddr=5.6.0 ipaddr-sexp=5.6.0 ipaddr.unix=5.6.0 liquidsoap-lang=2.2.5 liquidsoap-lang.console=2.2.5 liquidsoap_builtins liquidsoap_core liquidsoap_ffmpeg liquidsoap_mem_usage liquidsoap_memtrace liquidsoap_optionals liquidsoap_oss liquidsoap_posix_time liquidsoap_prometheus liquidsoap_runtime logs=0.7.0 logs.fmt=0.7.0 logs.lwt=0.7.0 lwt lwt.unix macaddr=5.6.0 magic-mime=1.3.1 mem_usage=0.1.1 memtrace=0.2.3 menhirLib=20240715 metadata=0.3.0 mm=0.8.6 mm.audio=0.8.6 mm.base=0.8.6 mm.image=0.8.6 mm.midi=0.8.6 mm.video=0.8.6 ocplib-endian ocplib-endian.bigstring pcre=7.5.0 posix-base=2.0.2 posix-time2=2.0.2 posix-time2.constants=2.0.2 posix-time2.stubs=2.0.2 posix-time2.types=2.0.2 posix-types=2.0.2 posix-types.constants=2.0.2 ppx_sexp_conv.runtime-lib=v0.16.0 prometheus=1.2 prometheus-app=1.2 re=1.12.0 result=1.5 sedlex=3.3 seq=[distributed with OCaml 4.07 or above] sexplib0=v0.16.0 stdlib-shims=0.3.0 str=[distributed with Ocaml] stringext=1.6.0 threads=[distributed with Ocaml] threads.posix=[internal] unix=[distributed with Ocaml] unix-errno=0.6.2 unix-errno.errno_bindings=0.6.2 unix-errno.errno_types=0.6.2 unix-errno.errno_types_detected=0.6.2 unix-errno.unix=0.6.2 uri=4.4.0 uri-sexp=4.4.0 uri.services=4.4.0
   - architecture        : amd64
   - host                : x86_64-pc-linux-musl
   - target              : x86_64-pc-linux-musl
   - system              : linux
   - ocamlopt_cflags     : -O2 -fno-strict-aliasing -fwrapv -pthread -fPIC
   - native_c_compiler   : gcc -O2 -fno-strict-aliasing -fwrapv -pthread -fPIC -D_FILE_OFFSET_BITS=64
   - native_c_libraries  : -lm

 * Configured paths
   - mode              : posix
   - standard library  : /usr/share/liquidsoap/libs
   - scripted binaries : /usr/share/liquidsoap/bin
   - rundir            : /var/run/liquidsoap
   - logdir            : /var/log/liquidsoap
   - camomile files    : /usr/share/liquidsoap/camomile

 * Supported input formats
   - MP3               : no (requires mad)
   - AAC               : no (requires faad)
   - Ffmpeg            : yes
   - Flac (native)     : no (requires flac)
   - Flac (ogg)        : no (requires ogg)
   - Opus              : no (requires opus)
   - Speex             : no (requires speex)
   - Theora            : no (requires theora)
   - Vorbis            : no (requires vorbis)

 * Supported output formats
   - FDK-AAC           : no (requires fdkaac)
   - Ffmpeg            : yes
   - MP3               : no (requires lame)
   - MP3 (fixed-point) : no (requires shine)
   - Flac (native)     : no (requires flac)
   - Flac (ogg)        : no (requires ogg)
   - Opus              : no (requires opus)
   - Speex             : no (requires speex)
   - Theora            : no (requires theora)
   - Vorbis            : no (requires vorbis)

 * Tags
   - Taglib (ID3 tags) : no (requires taglib)
   - Vorbis            : no (requires vorbis)

 * Input / output
   - ALSA              : no (requires alsa)
   - AO                : no (requires ao)
   - FFmpeg            : yes
   - GStreamer         : no (requires gstreamer)
   - JACK              : no (requires bjack)
   - OSS               : yes
   - Portaudio         : no (requires portaudio)
   - Pulseaudio        : no (requires pulseaudio)
   - SRT               : no (requires srt)

 * Audio manipulation
   - FFmpeg            : yes
   - LADSPA            : no (requires ladspa)
   - Lilv              : no (requires lilv)
   - Samplerate        : no (requires samplerate)
   - SoundTouch        : no (requires soundtouch)
   - StereoTool        : no (requires ctypes-foreign)

 * Video manipulation
   - camlimages        : no (requires camlimages)
   - FFmpeg            : yes
   - frei0r            : no (requires frei0r)
   - ImageLib          : no (requires imagelib)
   - SDL               : no (requires tsdl-image & tsdl-ttf)

 * MIDI manipulation
   - DSSI              : no (requires dssi)

 * Visualization
   - GD                : no (requires gd)
   - Graphics          : no (requires graphics)
   - SDL               : no (requires tsdl-image & tsdl-ttf)

 * Additional libraries
   - FFmpeg filters    : yes
   - FFmpeg devices    : yes
   - inotify           : yes
   - irc               : no (requires irc-client-unix)
   - jemalloc          : no (requires jemalloc)
   - lastfm            : no (requires lastfm)
   - lo                : no (requires lo)
   - memtrace          : yes
   - mem_usage         : yes
   - osc               : no (requires osc-unix)
   - ssl               : no (requires ssl)
   - tls               : no (requires tls-liquidsoap)
   - posix-time2       : yes
   - windows service   : no (requires winsvc)
   - YAML support      : no (requires yaml)
   - XML playlists     : no (requires xmlplaylist)

 * Monitoring
   - Prometheus        : yes

Results

Liquidsoap with jemalloc

With jemalloc, memory usage started at 155 MB and increased to 188 MB after 6 days. CPU usage stayed around 10% on average, with small spikes during heavy tasks.

• Memory usage: Starts at 155 MB and reaches 188 MB after 6 days.
• CPU usage: Average 10%, occasional spikes.

Liquidsoap without jemalloc

Without jemalloc, memory usage started at 150 MB and reached 183 MB after 6 days. CPU usage stayed around 10% on average, similar to the jemalloc version.

• Memory usage: Starts at 150 MB and reaches 183 MB after 6 days.
• CPU usage: Average 10%, occasional spikes.

Conclusion

Turning off jemalloc doesn’t make a big difference in performance. Memory usage is slightly lower without it, and CPU usage is the same in both setups. Synthetic tests showed a tiny increase in CPU (0.01% to 0.1%), but it wasn’t noticeable in real use.