[ardour-users] Latency: AGP vs PCI video card and XFS journalling vs not

[lee at fallingforward.net]

Your system has far better hardware than mine and I can get JACK down to
about 11ms latency with no dropouts. It seems our differences are that I
have an AGP video card and ext3 filesystem. I would highly recommend an
AGP video card, I got a Radeon 9000 new for US $80.

-lee

On Sun, 22 Feb 2004, Eric wrote:

> I have built a box that I thought would be able to support some very
> low-latency recording in the eventual hope of software monitoring with
> some effects in the loop (is anyone able to do this?).  It's a dual
> athlon 2400 w/ 1GB of DDR266, dual 10K SCSI drives, and my M-Audio
> Delta66.  I'm using the Debian unstable packages (jack 0.94 and ardour
> beta9+3) with a 2.6.3 kernel and have played around w/ all the
> standard latency issues (no extra stuff running, swapped PCI cards
> around for interrupts, etc.).  However, I'm not able to go lower than
> the default jack 3 periods of 1024 (with rt enabled, obviously) when
> working on my typical projects of 8-12 48KHz mono tracks, even without
> any effects in the loop.  It is dissapointing to have to go back to
> hardware monitoring w/ no effects...I have two questions:
>
> 1.  Could it be my old Voodoo3 PCI video card is hogging the bus?
> Rendering the mixer window definitely has an effect on my audio...if I
> drag it around or minimize/maximize it I can actually slow down the
> audio playback (which was surprising to me) or cause xruns and
> timeouts.  I've taken to just minimizing everything while I'm
> recording.  I didn't care about my graphics card, but now I'm
> considering an AGP one (nVidia GeoForceFX 5600 or ATI Radeon 9700)
> just to try and improve this...
>
> 2.  Could it be my XFS filesystems?  If I have 8 or so tracks on one
> drive, it can't even handle playback w/o giving disk errors.  I've
> tweaked all the XFS options, and currently have a large (64MB) log for
> each filesystem that resides on the opposite disk.  Would turning the
> log size up or down help?  Is there a way to just turn off journalling
> in XFS, or would ext2 be better?  I did notice that exporting to my
> default param (i.e. small log) ext3 root partition seems to be faster
> than to my XFS.
>
> --
> http://ir.iit.edu/~ej
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