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authorArnd Bergmann <arnd@arndb.de>2009-06-12 09:53:47 +0200
committerArnd Bergmann <arnd@arndb.de>2009-06-12 11:32:58 +0200
commit5b02ee3d219f9e01b6e9146e25613822cfc2e5ce (patch)
tree7ce9126738c3cf4b37d67170d0e4b34818c057a9 /Documentation/scheduler/sched-rt-group.txt
parent26a28fa4fea5b8c65713aa50c124f76a88c7924d (diff)
parent8ebf975608aaebd7feb33d77f07ba21a6380e086 (diff)
downloadop-kernel-dev-5b02ee3d219f9e01b6e9146e25613822cfc2e5ce.zip
op-kernel-dev-5b02ee3d219f9e01b6e9146e25613822cfc2e5ce.tar.gz
asm-generic: merge branch 'master' of torvalds/linux-2.6
Fixes a merge conflict against the x86 tree caused by a fix to atomic.h which I renamed to atomic_long.h. Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'Documentation/scheduler/sched-rt-group.txt')
-rw-r--r--Documentation/scheduler/sched-rt-group.txt20
1 files changed, 19 insertions, 1 deletions
diff --git a/Documentation/scheduler/sched-rt-group.txt b/Documentation/scheduler/sched-rt-group.txt
index 5ba4d3f..1df7f9c 100644
--- a/Documentation/scheduler/sched-rt-group.txt
+++ b/Documentation/scheduler/sched-rt-group.txt
@@ -4,6 +4,7 @@
CONTENTS
========
+0. WARNING
1. Overview
1.1 The problem
1.2 The solution
@@ -14,6 +15,23 @@ CONTENTS
3. Future plans
+0. WARNING
+==========
+
+ Fiddling with these settings can result in an unstable system, the knobs are
+ root only and assumes root knows what he is doing.
+
+Most notable:
+
+ * very small values in sched_rt_period_us can result in an unstable
+ system when the period is smaller than either the available hrtimer
+ resolution, or the time it takes to handle the budget refresh itself.
+
+ * very small values in sched_rt_runtime_us can result in an unstable
+ system when the runtime is so small the system has difficulty making
+ forward progress (NOTE: the migration thread and kstopmachine both
+ are real-time processes).
+
1. Overview
===========
@@ -169,7 +187,7 @@ get their allocated time.
Implementing SCHED_EDF might take a while to complete. Priority Inheritance is
the biggest challenge as the current linux PI infrastructure is geared towards
-the limited static priority levels 0-139. With deadline scheduling you need to
+the limited static priority levels 0-99. With deadline scheduling you need to
do deadline inheritance (since priority is inversely proportional to the
deadline delta (deadline - now).
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