[linux-audio-user] low latency

[Jesse Chappell]

Patrick Shirkey wrote on Fri, 16-May-2003:

 > For those of you who don't follow the jack list there was a recent 
 > (semi) discovery htat greatly improves performance for journalled 
 > filesystems.
 > 
 > The main problem is that jack writes data to a /tmp file. It has been 
 > found that mounting /tmp as tmpfs (in RAM) solves the problems that many 
 > people have experienced with lockups while using JACK.
 > 
 > Just put this in your /etc/fstab
 > 
 > none                /tmp              tmpfs     defaults      0 0
 > 
 
This needs to be more fully qualified.   These solutions reduce
the audio buffer overruns while using JACK under certain conditions.
It does not solve lockups.   The solutions mentioned above (and
below) help when your /tmp directory is mounted on a reiserfs
filesystem.  Whether or not it is necessary for other journalled
filesystems is not yet verified.

Note that mounting your /tmp on a tmpfs is not be done without 
due consideration.  You will need to have ample swap space available 
in the case where other applications may write very large files to 
the /tmp area.

The other (less intrusive) option to enable JACK to place its
FIFOs on a ram-based filesystem follows:
---------------------------------------------------------------
# mkdir /mnt/ramfs

[edit /etc/fstab and add the following line]
 none       /mnt/ramfs      tmpfs      defaults  0 0

Then use --with-default-tmpdir=/mnt/ramfs to the JACK configure
line when you build it.  No clients need to be recompiled.
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jlc