Forgot to 'reply to all', because it's *ever* so important everyone reads this...
-------- Original Message -------- Subject: Re: [PD] Low Latency patch for kernel 2.6.8.1 anyone? Date: Sun, 05 Sep 2004 22:34:46 -0700 From: Ian Smith-Heisters heisters@0x09.com To: thewade pdman@aproximation.org References: 200409060150.i861oonb024781@sanctuary.aproximation.org
Isn't low latency part of the kernel as of 2.6? If it's not automatically turned on, it's an option in the config. I guess I'm assuming you're talking about THE low latency patch that we used to use on 2.4, but perhaps you're looking for any new low latency patches...?
Congrats on the AMD 64, you lucky sod ;)
-ish
thewade wrote:
Is there a low latency patch for kernel 2.6.8.1? I have a new AMD 64 and I was hoping to see how fast it can go with PD...
Thanks for the help! -thewade
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On Mon, Sep 06, 2004 at 03:36:53PM EST, Ian Smith-Heisters wrote:
Isn't low latency part of the kernel as of 2.6? If it's not automatically turned on, it's an option in the config. I guess I'm assuming you're talking about THE low latency patch that we used to use on 2.4, but perhaps you're looking for any new low latency patches...?
You are thinking of the preemptable kernel config option. Unfortunately, wit this option turned on, it is still not possible to get as low a latency as it is on 2.4. There is however, a patch that is being worked on to address this issue, and while it is quite stable now, it still has some way to go, as more problems are being found all the time.
Check out the following URL for more info.
http://www.affenbande.org/~tapas/linux-2.6.x-ll.html
Luke Yelavich http://www.audioslack.com luke@audioslack.com
and a little note from ck's site about preemption in 2.6 for those who still wonder if they should use it or not.
"Preempt? I recommend disabling preemption in the kernel configuration unless you have a specific low latency requirement! It causes poorly written applications to misbehave far more. The gains in lateny with in-kernel preemption in 2.6 would not be noticable to a human, unlike 2.4 which had much larger latencies in the kernel. For serious audio work, video capture etc, you should enable preempt."
http://members.optusnet.com.au/ckolivas/kernel/
and interesting articles about preempt or not (so now you can get even more confused)
http://kerneltrap.org/node/view/2702
http://kerneltrap.org/node/view/3440
+! aym3ric.
ps: maybe it would be nice "one day" to try to gather pd "benchmarks" to see what the best could be taken from 2.6 kernels and how, everytime a latency talk is started it's always dying into mass-confusion. I think it would be really great to have online somewhere, a kernel recommandation guide for pd that has not be written for 2.4 and planet ccrma (no offense, just looking for fresh docs).
ps: i'm aware such talks are mostly happening in linux-audio lists, but my point here is to make this whole information friendly available for users, as a single note about recommanded software setup. This could be even extended to Gem and pdp/pidip, pointing on which drivers are the most efficient etc etc ... just a simple "pd setup guideline".
On Mon, Sep 06, 2004 at 01:19:50PM +1000, Luke Yelavich wrote :
On Mon, Sep 06, 2004 at 03:36:53PM EST, Ian Smith-Heisters wrote:
Isn't low latency part of the kernel as of 2.6? If it's not automatically turned on, it's an option in the config. I guess I'm assuming you're talking about THE low latency patch that we used to use on 2.4, but perhaps you're looking for any new low latency patches...?
You are thinking of the preemptable kernel config option. Unfortunately, wit this option turned on, it is still not possible to get as low a latency as it is on 2.4. There is however, a patch that is being worked on to address this issue, and while it is quite stable now, it still has some way to go, as more problems are being found all the time.
Check out the following URL for more info.
http://www.affenbande.org/~tapas/linux-2.6.x-ll.html
Luke Yelavich http://www.audioslack.com luke@audioslack.com
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Aymeric -
Ian Smith-Heisters -
Luke Yelavich