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documentation: Fix relation between nohz_full and rcu_nocbs

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If a CPU is specified in the nohz_full= kernel boot parameter to a
kernel built with CONFIG_NO_HZ_FULL=y, then that CPU's callbacks will
be offloaded, just as if that CPU had also been specified in the
rcu_nocbs= kernel boot parameter.  But the current documentation
states that the user must keep these two boot parameters manually
synchronized.  This commit therefore updates the documentation to
reflect reality.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-06-02 11:26:43 -07:00
parent 520eccdfe1
commit f99bcb2cdb
1 changed files with 4 additions and 3 deletions
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7
Documentation/admin-guide/kernel-parameters.txt
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@ -2633,9 +2633,10 @@
In kernels built with CONFIG_NO_HZ_FULL=y, set
the specified list of CPUs whose tick will be stopped
whenever possible. The boot CPU will be forced outside
the range to maintain the timekeeping.
The CPUs in this range must also be included in the
rcu_nocbs= set.
the range to maintain the timekeeping. Any CPUs
in this list will have their RCU callbacks offloaded,
just as if they had also been called out in the
rcu_nocbs= boot parameter.
noiotrap [SH] Disables trapped I/O port accesses.