Jim Cromie wrote:
PS. attached is an attempt to improve README.INSTALL along these and
other lines.
Please feel free to cut out the false parts ;-)
I think we should simply add a link from README.INSTALL to the
troubleshooting guide, where things are explained in length, for each
platforms.
------------------------------------------------------------------------
Index: README.INSTALL
===================================================================
--- README.INSTALL (revision 927)
+++ README.INSTALL (working copy)
@@ -74,6 +74,19 @@
Once the target kernel has been prepared, all Xenomai configuration
options are available from the "Real-time subsystem" toplevel menu.
+When configuring, you should *disable* PM (power management), ACPI,
+and CPU_FREQ. The 1st 2 invoke uninterruptible BIOS routines, which
+destroy the rt-determinism guarantees that you're presumably seeking.
+If you're curious, build it, install it, and run xeno-test, you'll
+likely see very large latencies. If you see otherwise, please email
+the evidence.
+
+CPU_FREQ is bad because it breaks some timing guarantees on some
+chips, and these problems are too varied/unpredictable to accomodate.
+For example, (my) Pentium-M laptop shows "cpu MHz : 600.000" at idle,
+but 1700 when compiling. Some TSCs also change frequency with the
+processor, making them useless if the clock is changing.
+
Once configured, the kernel should be built as usual.
It might be a good idea to put all the output into a different build
@@ -143,9 +156,11 @@
NAME DESCRIPTION [BINDING,]DEFAULT(*)
--enable-x86-sep Enable x86 SEP instructions strong,disabled
- for issuing syscalls
+ for issuing syscalls.
+ You will also need NPTL
--enable-x86-tsc Enable x86 TSC for timings strong,enabled
+ falls back to PIT if needed
Nope, the user-space support could not fallback properly to PIT if TSC
is activated using this switch. In the latter case, "rdtsc" insns will
be wired into the code, making it invalid for using with CPUs lacking a
timestamp counter.
--
Philippe.
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