diff options
author | James Bottomley <James.Bottomley@HansenPartnership.com> | 2009-06-12 10:02:03 -0500 |
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committer | James Bottomley <James.Bottomley@HansenPartnership.com> | 2009-06-12 10:02:03 -0500 |
commit | 82681a318f9f028ea64e61f24bbd9ac535531921 (patch) | |
tree | 529b6a5b4fd040fb54b7672b1a224ebd47445876 /Documentation/scheduler/sched-rt-group.txt | |
parent | 3860c97bd60a4525bb62eb90e3e7d2f02662ac59 (diff) | |
parent | 8ebf975608aaebd7feb33d77f07ba21a6380e086 (diff) |
[SCSI] Merge branch 'linus'
Conflicts:
drivers/message/fusion/mptsas.c
fixed up conflict between req->data_len accessors and mptsas driver updates.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Diffstat (limited to 'Documentation/scheduler/sched-rt-group.txt')
-rw-r--r-- | Documentation/scheduler/sched-rt-group.txt | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/Documentation/scheduler/sched-rt-group.txt b/Documentation/scheduler/sched-rt-group.txt index 5ba4d3fc625..1df7f9cdab0 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). |