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authorDavid S. Miller <davem@davemloft.net>2009-06-15 14:02:23 +0400
committerDavid S. Miller <davem@davemloft.net>2009-06-15 14:02:23 +0400
commit9cbc1cb8cd46ce1f7645b9de249b2ce8460129bb (patch)
tree8d104ec2a459346b99413b0b77421ca7b9936c1a /Documentation/scheduler/sched-rt-group.txt
parentca44d6e60f9de26281fda203f58b570e1748c015 (diff)
parent45e3e1935e2857c54783291107d33323b3ef33c8 (diff)
downloadlinux-9cbc1cb8cd46ce1f7645b9de249b2ce8460129bb.tar.xz
Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/torvalds/linux-2.6
Conflicts: Documentation/feature-removal-schedule.txt drivers/scsi/fcoe/fcoe.c net/core/drop_monitor.c net/core/net-traces.c
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 5ba4d3fc625a..1df7f9cdab05 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).