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authorLinus Torvalds <torvalds@linux-foundation.org>2009-06-10 15:32:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-10 15:32:59 -0700
commit99e97b860e14c64760855198e91d1166697131a7 (patch)
treefadc8368c3f784bff92fba82d983e7861559cf9d /Documentation
parent82782ca77d1bfb32b0334cce40a25b91bd8ec016 (diff)
parentf04d82b7e0c63d0251f9952a537a4bc4d73aa1a9 (diff)
Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: sched: fix typo in sched-rt-group.txt file ftrace: fix typo about map of kernel priority in ftrace.txt file. sched: properly define the sched_group::cpumask and sched_domain::span fields sched, timers: cleanup avenrun users sched, timers: move calc_load() to scheduler sched: Don't export sched_mc_power_savings on multi-socket single core system sched: emit thread info flags with stack trace sched: rt: document the risk of small values in the bandwidth settings sched: Replace first_cpu() with cpumask_first() in ILB nomination code sched: remove extra call overhead for schedule() sched: use group_first_cpu() instead of cpumask_first(sched_group_cpus()) wait: don't use __wake_up_common() sched: Nominate a power-efficient ilb in select_nohz_balancer() sched: Nominate idle load balancer from a semi-idle package. sched: remove redundant hierarchy walk in check_preempt_wakeup
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/scheduler/sched-rt-group.txt20
-rw-r--r--Documentation/trace/ftrace.txt15
2 files changed, 31 insertions, 4 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).
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index fd9a3e693813..e362f50c496f 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -518,9 +518,18 @@ priority with zero (0) being the highest priority and the nice
values starting at 100 (nice -20). Below is a quick chart to map
the kernel priority to user land priorities.
- Kernel priority: 0 to 99 ==> user RT priority 99 to 0
- Kernel priority: 100 to 139 ==> user nice -20 to 19
- Kernel priority: 140 ==> idle task priority
+ Kernel Space User Space
+ ===============================================================
+ 0(high) to 98(low) user RT priority 99(high) to 1(low)
+ with SCHED_RR or SCHED_FIFO
+ ---------------------------------------------------------------
+ 99 sched_priority is not used in scheduling
+ decisions(it must be specified as 0)
+ ---------------------------------------------------------------
+ 100(high) to 139(low) user nice -20(high) to 19(low)
+ ---------------------------------------------------------------
+ 140 idle task priority
+ ---------------------------------------------------------------
The task states are: