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rcu: Eliminate NOCBs CPU-state Kconfig options

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The CONFIG_RCU_NOCB_CPU_ALL, CONFIG_RCU_NOCB_CPU_NONE, and
CONFIG_RCU_NOCB_CPU_ZERO Kconfig options are used only in testing and
are redundant with the rcu_nocbs= boot parameter.  This commit therefore
removes these three Kconfig options and adjusts the rcutorture scripts
to use the boot parameter instead.

Signed-off-by: Paul E. McKenney <[email protected]>
This commit is contained in:
Paul E. McKenney 2017-05-15 16:26:34 -07:00
commit 44c65ff2e3
11 changed files with 26 additions and 131 deletions
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53
init/Kconfig
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@ -709,59 +709,6 @@ config RCU_NOCB_CPU
Say Y here if you want to help to debug reduced OS jitter.
Say N here if you are unsure.
choice
prompt "Build-forced no-CBs CPUs"
default RCU_NOCB_CPU_NONE
depends on RCU_NOCB_CPU
help
This option allows no-CBs CPUs (whose RCU callbacks are invoked
from kthreads rather than from softirq context) to be specified
at build time. Additional no-CBs CPUs may be specified by
the rcu_nocbs= boot parameter.
config RCU_NOCB_CPU_NONE
bool "No build_forced no-CBs CPUs"
help
This option does not force any of the CPUs to be no-CBs CPUs.
Only CPUs designated by the rcu_nocbs= boot parameter will be
no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
kthreads whose names begin with "rcuo". All other CPUs will
invoke their own RCU callbacks in softirq context.
Select this option if you want to choose no-CBs CPUs at
boot time, for example, to allow testing of different no-CBs
configurations without having to rebuild the kernel each time.
config RCU_NOCB_CPU_ZERO
bool "CPU 0 is a build_forced no-CBs CPU"
help
This option forces CPU 0 to be a no-CBs CPU, so that its RCU
callbacks are invoked by a per-CPU kthread whose name begins
with "rcuo". Additional CPUs may be designated as no-CBs
CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
All other CPUs will invoke their own RCU callbacks in softirq
context.
Select this if CPU 0 needs to be a no-CBs CPU for real-time
or energy-efficiency reasons, but the real reason it exists
is to ensure that randconfig testing covers mixed systems.
config RCU_NOCB_CPU_ALL
bool "All CPUs are build_forced no-CBs CPUs"
help
This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
boot parameter will be ignored. All CPUs' RCU callbacks will
be executed in the context of per-CPU rcuo kthreads created for
this purpose. Assuming that the kthreads whose names start with
"rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
on the remaining CPUs, but might decrease memory locality during
RCU-callback invocation, thus potentially degrading throughput.
Select this if all CPUs need to be no-CBs CPUs for real-time
or energy-efficiency reasons.
endchoice
endmenu # "RCU Subsystem"
config BUILD_BIN2C