Subject: [linux-audio-dev] new preemptive kernel-patch from Montavista available
From: Benno Senoner (sbenno_AT_gardena.net)
Date: Thu Nov 23 2000 - 14:55:17 EET
Hi,
Andrew Morton informed me that Montavista has released a new
preemptive kernel, which seems to achieve 2msec latencies when
running latencytest. (I haven't tested it yet).
I'm attaching Nigel's message below.
Anyway Nigel says:
"However, there are still some >10ms non-preemptible paths that are not
exercised by this test."
It would be interesting to know how Andrews 2.4-LL patches compare to
the premeptive ones.
(eg what are the longest non-preemptable paths in that case ?)
cheers,
Benno.
http://boudicca.tux.org/hypermail/linux-kernel/this-week/0681.html
--------
From: Nigel Gamble (nigel_AT_nrg.org)
Date: Wed Nov 22 2000 - 19:04:05 EST
Subject: Latest preemptible kernel (low latency) patch available
MontaVista Software's latest preemptible kernel patch,
preempt-2.4.0-test11-1.patch.bz2, is now available in
ftp://ftp.mvista.com/pub/Area51/preemptible_kernel/
Here is an extract from the README file:
The patches in this directory, when applied to the corresponding
kernel source, will define a new configure option, 'Preemptable Kernel',
under the 'Processor type and features' section. When enabled, and the
kernel is rebuilt it will be fully preemptable, subject to SMP lock
areas (i.e. it uses SMP locking on a UP to control preemptability).
The patch can only be enabled for ix86 uniprocessor platforms.
(Stay tuned for other platforms and SMP support.)
Notes for preempt-2.4.0-test11-1.patch
--------------------------------------
- Updated to kernel 2.4.0-test11
Notes for preempt-2.4.0-test10-1.patch
--------------------------------------
The main changes between this and previous patches are:
- Updated to kernel 2.4.0-test10
- Long held spinlocks changed into mutex locks, currently implemented
using semaphores. (We are working on a fast, priority inheriting,
binary semaphore implementation of these locks.)
The patch gives good results on Benno's Audio-Latency test
http://www.gardena.net/benno/linux/audio/, with maximum
latencies less than a couple of milliseconds recorded
using a 750MHz PIII machine. However, there are still
some >10ms non-preemptible paths that are not exercised
by this test.
The worst non-preemtible paths are now dominated by the big
kernel lock, which we hope can be completely eliminated in 2.5
by finer grained locks.
(I will be at the Linux Real-Time Workshop in Orlando next week, and
may not be able to access my work email address (nigel_AT_mvista.com),
which is why I'm posting this from my personal address.)
Nigel Gamble nigel_AT_nrg.org
Mountain View, CA, USA. http://www.nrg.org/
This archive was generated by hypermail 2b28 : Thu Nov 23 2000 - 13:57:28 EET