[linux-audio-user] 2.6.13 kernel: which patches for better latency

Eric Dantan Rzewnicki rzewnickie at rfa.org
Tue Sep 13 16:45:19 EDT 2005

On Mon, Sep 12, 2005 at 03:39:14PM -0500, Reuben Martin wrote:
> On 9/12/05, Reuben Martin <reuben.m at gmail.com> wrote:
> > On 9/12/05, Eric Dantan Rzewnicki <rzewnickie at rfa.org> wrote:
> > > On Thu, Sep 08, 2005 at 08:38:02PM -0500, Reuben Martin wrote:
> > > > On 9/7/05, guy <sayhi2guy at tiscali.co.uk> wrote:
> > > For historical clarification ( and someone correct me if I'm wrong on
> > > any of this ), Ingo did a set of low latency patches for 2.2/2.4 that
> > > basically showed that breaking up long code pathes could improve linux's
> > > latency performance. These were proof of concept patches, in a sense,
> > > but not accepted, nor intended, for the mainline kernel.
> > > Andrew Morton created a smaller and more tightly focused set of
> > > long-code-path-splitting low-latency patches for 2.4 inspired by Ingo's
> > > earlier work. These were intended to find an approach to achieving
> > > low-latency more acceptable to the kernel devs.
> > > Robert Love created a set of Preemption patches for 2.4 that were
> > > commonly applied along with Andrew's LL patches. The preemption patches
> > > were a different approach to achieve low-latency which allowed code
> > > paths which might run for a long time to be marked as pre-emptible.
> > I know all three of them contributed. I'm not sure who's was merged
> > into 2.5. I remember I used to use a combination of two diffferent
> > latency patch sets.

Yeah. I think it was a combination of all of their efforts. Andrew
maintained the LL (low latency) patches and Robert maintained the PE
(pre-empt) though they and others may have contributed to either or both

I remember naming my kernels something like 2.4.19-pe-ll, or some such.

> > > Much of Andrew and Robert's work on 2.4 was incorporated into the 2.5
> > > development kernel and thus the 2.6 series. However there were still
> > > latency problems with 2.6, so Ingo has again taken the lead in producing
> > > the current series of realtime-preemption patches. A lot of this work is
> > > now present in the mainline 2.6.13.x kernel.
> > If I understand correctly, chunks of his patch are slowly absorbed
> > into the mainline a bit at a time while he continues to keep finding
> > ways to shorten the length of code paths.

That is also my understanding of Ingo's current patch set's adoption
into the mainline.

Eric Dantan Rzewnicki  |  Systems Administrator
Technical Operations Division  |  Radio Free Asia
2025 M Street, NW  |  Washington, DC 20036  |  202-530-4900
This e-mail message is intended only for the use of the addressee and
may contain information that is privileged and confidential. Any 
unauthorized dissemination, distribution, or copying is strictly 
prohibited. If you receive this transmission in error, please contact
network at rfa.org.

More information about the Linux-audio-user mailing list