diff options
Diffstat (limited to 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 66 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-per-CPU-kthreads.rst | 2 |
2 files changed, 53 insertions, 15 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 36b83a47e54a..3483ac7f019d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4343,19 +4343,30 @@ Disable the Correctable Errors Collector, see CONFIG_RAS_CEC help text. - rcu_nocbs= [KNL] - The argument is a cpu list, as described above. - - In kernels built with CONFIG_RCU_NOCB_CPU=y, set - the specified list of CPUs to be no-callback CPUs. - Invocation of these CPUs' RCU callbacks will be - offloaded to "rcuox/N" kthreads created for that - purpose, where "x" is "p" for RCU-preempt, and - "s" for RCU-sched, and "N" is the CPU number. - This reduces OS jitter on the offloaded CPUs, - which can be useful for HPC and real-time - workloads. It can also improve energy efficiency - for asymmetric multiprocessors. + rcu_nocbs[=cpu-list] + [KNL] The optional argument is a cpu list, + as described above. + + In kernels built with CONFIG_RCU_NOCB_CPU=y, + enable the no-callback CPU mode, which prevents + such CPUs' callbacks from being invoked in + softirq context. Invocation of such CPUs' RCU + callbacks will instead be offloaded to "rcuox/N" + kthreads created for that purpose, where "x" is + "p" for RCU-preempt, "s" for RCU-sched, and "g" + for the kthreads that mediate grace periods; and + "N" is the CPU number. This reduces OS jitter on + the offloaded CPUs, which can be useful for HPC + and real-time workloads. It can also improve + energy efficiency for asymmetric multiprocessors. + + If a cpulist is passed as an argument, the specified + list of CPUs is set to no-callback mode from boot. + + Otherwise, if the '=' sign and the cpulist + arguments are omitted, no CPU will be set to + no-callback mode from boot but the mode may be + toggled at runtime via cpusets. rcu_nocb_poll [KNL] Rather than requiring that offloaded CPUs @@ -4599,8 +4610,12 @@ in seconds. rcutorture.fwd_progress= [KNL] - Enable RCU grace-period forward-progress testing + Specifies the number of kthreads to be used + for RCU grace-period forward-progress testing for the types of RCU supporting this notion. + Defaults to 1 kthread, values less than zero or + greater than the number of CPUs cause the number + of CPUs to be used. rcutorture.fwd_progress_div= [KNL] Specify the fraction of a CPU-stall-warning @@ -4801,6 +4816,29 @@ period to instead use normal non-expedited grace-period processing. + rcupdate.rcu_task_collapse_lim= [KNL] + Set the maximum number of callbacks present + at the beginning of a grace period that allows + the RCU Tasks flavors to collapse back to using + a single callback queue. This switching only + occurs when rcupdate.rcu_task_enqueue_lim is + set to the default value of -1. + + rcupdate.rcu_task_contend_lim= [KNL] + Set the minimum number of callback-queuing-time + lock-contention events per jiffy required to + cause the RCU Tasks flavors to switch to per-CPU + callback queuing. This switching only occurs + when rcupdate.rcu_task_enqueue_lim is set to + the default value of -1. + + rcupdate.rcu_task_enqueue_lim= [KNL] + Set the number of callback queues to use for the + RCU Tasks family of RCU flavors. The default + of -1 allows this to be automatically (and + dynamically) adjusted. This parameter is intended + for use in testing. + rcupdate.rcu_task_ipi_delay= [KNL] Set time in jiffies during which RCU tasks will avoid sending IPIs, starting with the beginning diff --git a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst index 5e51ee5b0358..e4a5fc26f1a9 100644 --- a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst +++ b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst @@ -208,7 +208,7 @@ Do at least one of the following: 2. Enable RCU to do its processing remotely via dyntick-idle by doing all of the following: - a. Build with CONFIG_NO_HZ=y and CONFIG_RCU_FAST_NO_HZ=y. + a. Build with CONFIG_NO_HZ=y. b. Ensure that the CPU goes idle frequently, allowing other CPUs to detect that it has passed through an RCU quiescent state. If the kernel is built with CONFIG_NO_HZ_FULL=y, |