Messages in this thread | | | Date | Tue, 4 Jan 2005 11:05:23 +0100 | From | Ingo Molnar <> | Subject | Re: Latency results with 2.6.10 - looks good |
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* Lee Revell <rlrevell@joe-job.com> wrote:
> Followup: other audio users have confirmed that 2.6.10 is the best > release yet latency-wise. It works most of the time at 64 frames > (~1.33ms latency). > > Now, the bad news: there are still enough xruns to make it not quite > good enough for, say, a recording studio; as we all know with realtime > constraints the worst case scenario is important. As expected the RT > kernel beats it by a wide margin. I have attached some numbers, > excerpted from a post by Rui on the JACK list. The JACK test used was > described previously on this list. > > Ingo, what are your plans for pushing more of the RT patch set > upstream? It seems that the soft/hardirq threading and voluntary > preemption (turning the might_sleep checks into preemption points) are > required to further improve the latency of the standard kernel. These > are well tested at this point and also zero cost for users who don't > enable them. I think if these features go upstream before 2.6.11 then > we can say all of the issues Paul raised, in that post months ago that > led to the VP patches, will be put to rest.
for 2.6.11 we have dozens of scheduler patches queued in -mm that do half of the work necessary for the rest of -RT. I'll split out more stuff from -RT once the scheduler queue in -mm gets smaller (i.e. once it gets merged upstream), but there's a natural limit to the rate of merging in a given subsystem, if we push things too hard it will deteriorate.
also, there's the necessary merging of preempt-bkl patch. It makes little sense to add the more advanced stuff when the BKL is allowed to generate up to ~200 milliseconds latencies. Hardirq and softirq threading would be the next step after that point.
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