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Diffstat (limited to 'Documentation/timers/NO_HZ.txt')
| -rw-r--r-- | Documentation/timers/NO_HZ.txt | 29 |
1 files changed, 3 insertions, 26 deletions
diff --git a/Documentation/timers/NO_HZ.txt b/Documentation/timers/NO_HZ.txt index 6eaf576294f3..2dcaf9adb7a7 100644 --- a/Documentation/timers/NO_HZ.txt +++ b/Documentation/timers/NO_HZ.txt @@ -194,32 +194,9 @@ that the RCU callbacks are processed in a timely fashion. Another approach is to offload RCU callback processing to "rcuo" kthreads using the CONFIG_RCU_NOCB_CPU=y Kconfig option. The specific CPUs to -offload may be selected via several methods: - -1. One of three mutually exclusive Kconfig options specify a - build-time default for the CPUs to offload: - - a. The CONFIG_RCU_NOCB_CPU_NONE=y Kconfig option results in - no CPUs being offloaded. - - b. The CONFIG_RCU_NOCB_CPU_ZERO=y Kconfig option causes - CPU 0 to be offloaded. - - c. The CONFIG_RCU_NOCB_CPU_ALL=y Kconfig option causes all - CPUs to be offloaded. Note that the callbacks will be - offloaded to "rcuo" kthreads, and that those kthreads - will in fact run on some CPU. However, this approach - gives fine-grained control on exactly which CPUs the - callbacks run on, along with their scheduling priority - (including the default of SCHED_OTHER), and it further - allows this control to be varied dynamically at runtime. - -2. The "rcu_nocbs=" kernel boot parameter, which takes a comma-separated - list of CPUs and CPU ranges, for example, "1,3-5" selects CPUs 1, - 3, 4, and 5. The specified CPUs will be offloaded in addition to - any CPUs specified as offloaded by CONFIG_RCU_NOCB_CPU_ZERO=y or - CONFIG_RCU_NOCB_CPU_ALL=y. This means that the "rcu_nocbs=" boot - parameter has no effect for kernels built with RCU_NOCB_CPU_ALL=y. +offload may be selected using The "rcu_nocbs=" kernel boot parameter, +which takes a comma-separated list of CPUs and CPU ranges, for example, +"1,3-5" selects CPUs 1, 3, 4, and 5. The offloaded CPUs will never queue RCU callbacks, and therefore RCU never prevents offloaded CPUs from entering either dyntick-idle mode |