http://rt.wiki.kernel.org/index.php/CONFIG_PREEMPT_RT_Patch
CONFIG PREEMPT RT Patch
From RTwiki
The CONFIG_PREEMPT_RT Patch Set
The CONFIG_PREEMPT_RT patch set
is maintained by a small group of core developers, led by Ingo Molnar.
This patch allows nearly all of the kernel to be preempted, with the
exception of a few very small regions of code ("raw_spinlock critical
regions"). This is done by replacing most kernel spinlocks with mutexes
that support priority inheritance, as well as
moving all interrupt and software interrupts to kernel threads.
The CONFIG_PREEMPT_RT patch set is also maintained in a git repo at kernel.org.
You can find now a detailed RT_PREEMPT_HOWTO on this page.
Paul McKenney has written a good CONFIG_PREEMPT_RT
overview which is a good introduction to the changes introduced to
the kernel by the CONFIG_PREEMPT_RT patch.
Download
The patch set is available here, as either a single monolithic patch, or in a
broken-out tarball. See the announcement regarding the broken-out patch
set.
There is also an apt repository for Ubuntu with x86 precompiled
kernel. You can find more information in this wiki page:
https://wiki.ubuntu.com/RealTime
Sending patches
Please send patches for the CONFIG_PREEMPT_RT Patch Set to LKML and
put Ingo Molnar and Thomas Gleixner on CC.
Please do not send clocksource and clockevents related patches
against the -rt patch. Make sure they apply against
Linus' tree.
Platforms Tested and in Use with
CONFIG_PREEMPT_RT
| Processor |
Model #'s |
Kernel version(s) |
Contact(s) |
Comment(s)
|
| Opteron |
IBM LS-20, LS-21, x3455 |
2.6.16-rt22, 2.6.20-rt8 |
Theodore Ts'o, Darren Hart |
|
| Xeon |
IBM 6850-P4U |
2.6.20-rt8, 2.6.21-rc6-rt0 |
Dave Sperry
|
|
| Intel Xeon 2.4GHz with HT |
HP xw8000 |
2.6.29.3-rt12 |
Raphaël
Doursenaud |
|
| AMD Opteron 175 |
ASUS A8N-SLI Premium |
2.6.29.3-rt12 |
Raphaël
Doursenaud |
|
| P4 |
Compaq Evo N610 |
2.6.16-rt22 |
Dave Sperry
|
|
| P3 |
Celeron 1300 |
2.6.21.5-rt14 |
Oleksandr
Natalenko |
|
| Intel |
Pentium Dual-Core T2330 |
2.6.29.1-rt4 |
Oleksandr
Natalenko |
|
| Prescott |
PentiumD 3 GHz |
2.6.22.6-rt9 |
Dmitry
Pisklov |
|
| Intel |
Pentium 4 2.4 GHz |
2.6.23.9-rt12 |
Jaswinder Singh |
|
| Intel |
Pentium 4 2.8 GHz with HT |
2.6.23.9-rt12 |
Jaswinder Singh |
|
| Intel |
FSC D2151S Celeron D 2.93 Ghz |
2.6.20-rt8 |
Remy Bohmer |
Avg. latency < 10us, worst case latency: < 30us (see
Note 1)
|
| Intel |
FSC D2151S Core 2 Duo E6300 |
2.6.20-rt8 |
Remy Bohmer |
Avg. latency < 10us, worst case latency: < 30us (see
Note 1)
|
| Intel |
Asus P5B Core 2 Duo E6600 2.4GHz |
2.6.23-rc4-rt1 |
Remy Bohmer |
Avg. latency < 10us, worst case latency: < 30us (see
Note 1)
|
| Intel |
Core 2 Quad Q6600 |
2.6.24.7-rt27 |
User:Pauls |
Works ok, but frequency scaling has to be turned off for
decent
results. A task run at 1 kHz repetition rate with low load was found to
be t-distributed with 4 degrees of freedom, with 1% value 0.9842 ms,
99% value 1.0103 ms (ideal realtime performance would get exactly 1 ms
for both values), with the frequency governor set to "performance".
|
| Intel Core 2 Quad Q6600 |
Gigabyte EP35C-DS3R |
2.6.29.3-rt13 |
Raphaël
Doursenaud |
|
| Intel |
IBM Thinkpad T43 Pentium M CPU 2 GHz |
2.6.23-rt3 |
PhilK |
Avg. latency < 14us, worst case latency: < 32us
|
| Intel |
Pentium 4 (M) 1.8 GHz |
2.6.29.1-rt7 |
Matthias Kaehlcke |
|
| ARM9 (v4t) |
Atmel AT91RM9200-EK (See AT91-Notes) |
2.6.23.12-rt14 |
Remy Bohmer |
worst case latency: < 300us (see Note 1)
|
| ARM9 (v4t) |
FREE_ECB_AT91 (See AT91-Notes) |
2.6.23.12-rt14 |
Carlos Camargo |
|
| ARM9 (v4t) |
Cirrus EP9301 |
2.6.29.1-rt7 |
Matthias Kaehlcke
|
| ARM9 (v5tej) |
Atmel AT91SAM9261 (See AT91-Notes) |
2.6.24.7-rt27 |
Remy Bohmer |
worst case latency: < 150us (see Note 1)
|
| ARM9 (v5tej) |
TI OMAP5912
OSK |
2.6.23-rt1 |
OMAP ML |
A small additional OMAP specific patch on top of -rt is
needed. See ML.
|
| ARM9 (v5tej) |
TI DM6446 DaVinci |
2.6.23-rt1 |
DaVinci ML |
A small additional DaVinci specific patch on top of -rt is
needed. See ML.
|
| ARM9 (v5tej) |
TS-7800 Marvell MV88F5182 ARM9 500MHz |
2.6.29.3-rt13 |
Stefan Agner
|
worst case latency: < 250us, see agner.ch
(german)
|
| SH4 |
Renesas R2D/R2D+ SH7751R CPU |
2.6.21-rt2 and later |
linux-sh
ML
|
Note 1: latency is defined as the time between the moment an
interrupt occurs in hardware, and the moment the corresponding
interrupt-thread gets running.
AT91-Notes: The following issues are known on this
architecture:
- Priority Inheritance Mutexes in userspace
(PTHREAD_PRIO_INHERIT) only works since 2.6.23-rt1 with Glibc 2.5 and
higher. Tested and stable with applications that match the memory
locking scheme described on HOWTO:_Build_an_RT-application.
- Clocksource and clockevent implementations are available, and
are in mainline since 2.6.24-rc4. (or see AT91-patchset)
Tickless and HRT both work, but not using them due to very high CPU
load compared to a ticking kernel on preempt-rt.
GPIO Interrupt handling is not stable which causes missing GPIO
interrupts, fixed by patch.
This patch is integrated in 2.6.23.11-rt14 and newer (Without this
patch, the Ethernet adapter (DM9000) on AT91SAM9261-EK does not work in
combination with PREEMPT-RT.)
