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ftrace: fix typo about map of kernel priority in ftrace.txt file.

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Fix typo about chart to map the kernel priority to user land priorities.

   * About sched_setscheduler(2)
      Processes scheduled under SCHED_FIFO or SCHED_RR
      can have a (user-space) static priority in the range 1 to 99.
      (reference: http://www.kernel.org/doc/man-pages/online/pages/
                  man2/sched_setscheduler.2.html)

   * From: Steven Rostedt
      0 to 98 - maps to RT tasks 99 to 1 (SCHED_RR or SCHED_FIFO)

      99 - maps to internal kernel threads that want to be lower than RT tasks
      but higher than SCHED_OTHER tasks. Although I'm not sure if any
      kernel thread actually uses this. I'm not even sure how this can be
      set, because the internal sched_setscheduler function does not allow
      for it.

      100 to 139 - maps nice levels -20 to 19. These are not set via
      sched_setscheduler, but are set via the nice system call.

      140 - reserved for idle tasks.

Signed-off-by: GeunSik Lim <geunsik.lim@samsung.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
GeunSik Lim 2009-05-28 10:36:11 +09:00 committed by Ingo Molnar
parent 4200efd9ac
commit 294ae40115
1 changed files with 12 additions and 3 deletions
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15
Documentation/trace/ftrace.txt
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@ -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: