[linux-audio-dev] nice [was: jack, low latency and IO]

[Jack O'Quin]

Jens M Andreasen <jens.andreasen at chello.se> writes:

> I have bitched the Mandrake-team for shipping a version/config of jack
> that cannot work. It appears like it might be the jack-team that is (at
> least partially) to blame ... (?)

If you discover a bug in JACK, please open a report...

  http://jackit.sourceforge.net/mantis/

> I said that they (Mandrake) set up jack to have its sockets on /tmp,
> which cannot work when /tmp is part of journaling file-system.

Perhaps they should configure using --with-default-tmpdir=PATH.  The
default path, /tmp, is not usually the best choice, but has the major
advantage of being present on every system.  For a default, that's
good.  

Distribution makers may have reason to know that a better option is
available.  Some use /dev/shm, which is needed for POSIX shared memory
support and therefore often configured correctly.  Beware, however,
that compiling JACK to use POSIX shared memory will conflict with that
choice.

> After that, I have had a look at various options that are available in a
> clickedeclick style after install. One of them is to empty /tmp on
> reboot.
> 
> At first I thought that this option would do
> 
> # rm /tmp/*
> 
> .. or some such. Apparently not because when i do df:
> 
> -------------------------------------------------------
> [jens at elephant jens]$ df
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/hda5             3,4G  2,2G  1,1G  69% /
> /dev/hda7             4,3G  2,0G  2,3G  47% /home
> none                  126M     0  126M   0% /mnt/ramfs
> /dev/hda1             1,6G  1,4G  207M  87% /mnt/windows
> none                  126M   68K  126M   1% /tmp
> -------------------------------------------------------
> 
> ... , it should be clear that /tmp is now similar to /mnt/ramfs (which
> is the one I created from the guidelines in the jack source-
> distribution.)

A better check is probably something like this...

 $ grep tmp /etc/fstab
/dev/hda8	/tmp		ext2	defaults		0	2
none		/dev/shm	tmpfs	defaults		0	0
jack		/tmp/jack	tmpfs	defaults		0	0

You want it to say `tmpfs' (or maybe `ramfs').

> [jens at elephant jens]$ /usr/bin/jackd --version
> jackd version 0.98.1
> default tmp directory: /tmp
> 
> ... and:
> 
> [jens at elephant jens]$ /usr/local/bin/jackd --version
> jackd version 0.99.0 tmpdir /mnt/ramfs protocol 13
> 
> ... , then I get the impression that something very positive happened
> between jackd_0.98.1 and jackd_0.99.0
> 
> Comments?

Mixing two different versions of JACK on the same system is usually a
disaster.  Programs linked with /usr/lib/libjack.so.0 will generally
not work correctly with /usr/local/bin/jackd.
-- 
  joq