Subject: Re: [linux-audio-user] rtc patching
From: Josh Green (jgreen_AT_users.sourceforge.net)
Date: Fri Sep 14 2001 - 07:12:27 EEST
On Fri, 14 Sep 2001 13:08:46 +1000
Andre Pang <ozone_AT_algorithm.com.au> wrote:
> On Thu, Sep 13, 2001 at 10:18:11AM -0300, Christian Lyra
> wrote:
>
> > If you are using a 2.4.x kernel you dont need a patch.
> Just do a make
> > xconfig, and select "Enable Real Time Clock Support"
> under "Character
> > devices". If you are not used to compile your own
> kernel, it's a good ideia
> > to read some docs before trying to do it :-)
>
> sorry for a stupid question, but does enabling RTC help
> latency
> or audio applications in general? i'm currently running
> Andrew
> Morton's low-latency patch for 2.4.9 with some other
> patches and
> latency on this computer is still through the roof; i'm
> wondering if that's because i haven't turned on
> CONFIG_RTC, or
> whether because the other patches are interfering.
>
>
> --
> #ozone/algorithm <ozone_AT_algorithm.com.au> -
> trust.in.love.to.save
The RTC helps only for programs that use it. It just
provides a nice time event source for doing time critical
things like MIDI sequencing, etc. It doesn't really relate
to latency. If your latency is still bad after applying
Andrew Morton's patch then make sure that you actually
enabled it "Low Latency Scheduling" and if you checked the
"Control low latency with sysctl" that you do a "echo '1'
>/proc/sys/kernel/lowlatency" to enable it on boot or
whenever you feel like it :) Hard disk access can be a major
source of latency spikes, make sure you are running it in
DMA mode. Dave Philips wrote a good article on Linux Low
Latency, you can find it here:
http://linux.oreillynet.com/pub/a/linux/2000/11/17/low_latency.html
Hope you can figure out whats causing your latency problems.
Benno's latencytest program is one way to test your system
(Dave's article talks about this). Lates..
Josh Green
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