[linux-audio-user] Re: [a-users] Re: [a-devel] File system and Voluntary Kernel Preemption

Lee Revell rlrevell at joe-job.com
Thu Jul 15 23:55:04 EDT 2004


On Thu, 2004-07-15 at 04:53, Damien Cirotteau wrote:
> On Thu, Jul 15, 2004 at 10:35:47AM +0200, Free Ekanayaka wrote :
> > |--==> "DC" == Damien Cirotteau <damien.cirotteau at agnula.org> writes:
> > 
> >   DC> Hi all, 
> >   DC> some very interesting links submited by simmo on IRC
> > 
> >   DC> File system:
> >   DC> http://kerneltrap.org/node/view/3466
> > 
> >   DC> Voluntary Kernel Preemption:
> >   DC> http://kerneltrap.org/node/view/3440
> > 
> > Yes these are definitively interesting!
> > 
> > I'll read them carefully and see if we can adopt some new trick :)
> 
> Two first thing that i can retain:
> - Don't use reseirfs for now (especially with 2.6)
> - Enable CONFIG_SND_DEBUG  in the kernel so  it will be  easier to trace
> the xruns. It looks that it is a very useful feature to understand where
> the xruns comes from and is very good feedback to send to kernel folks

The intrepid user in need of low latency should try 2.6.8-rc1-mm1.  I
sent a bunch of XRUN traces to Andrew Morton, and this kernel contains
numerous latency fixes as a result.  Some of these fixes were to
extremely important areas (get_user_pages, a fix for
framebuffer-scrolling issue, and more).  The improvement should be
major.  He is going to be unavailable until July 26th, so the next few
weeks are a great opportunity to test and collect data.

You are correct in that reiserfs as shipped with the kernel should
probably not be used for now if you need low latency.  However, I
strongly suspect that SuSe (which users reiser by default) contains
fixes for this which are not in the mainstream kernel.  By enabling
CONFIG_SND_DEBUG *and* turning on XRUN debugging at runtime (echo 2 >
proc/asound/cardX/pcmX/xrun_debug) you will be able to see whether this
is affecting you.

Here is the announcement:

http://www.ussg.iu.edu/hypermail/linux/kernel/0407.1/1453.html

Lee



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