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-rw-r--r--Documentation/kernel-parameters.txt50
1 files changed, 36 insertions, 14 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 705fb915cbf7..a1489e14f8ee 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -33,6 +33,37 @@ can also be entered as
Double-quotes can be used to protect spaces in values, e.g.:
param="spaces in here"
+cpu lists:
+----------
+
+Some kernel parameters take a list of CPUs as a value, e.g. isolcpus,
+nohz_full, irqaffinity, rcu_nocbs. The format of this list is:
+
+ <cpu number>,...,<cpu number>
+
+or
+
+ <cpu number>-<cpu number>
+ (must be a positive range in ascending order)
+
+or a mixture
+
+<cpu number>,...,<cpu number>-<cpu number>
+
+Note that for the special case of a range one can split the range into equal
+sized groups and for each group use some amount from the beginning of that
+group:
+
+ <cpu number>-cpu number>:<used size>/<group size>
+
+For example one can add to the command line following parameter:
+
+ isolcpus=1,2,10-20,100-2000:2/25
+
+where the final item represents CPUs 100,101,125,126,150,151,...
+
+
+
This document may not be entirely up to date and comprehensive. The command
"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
module. Loadable modules, after being loaded into the running kernel, also
@@ -1789,13 +1820,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
See Documentation/filesystems/nfs/nfsroot.txt.
irqaffinity= [SMP] Set the default irq affinity mask
- Format:
- <cpu number>,...,<cpu number>
- or
- <cpu number>-<cpu number>
- (must be a positive range in ascending order)
- or a mixture
- <cpu number>,...,<cpu number>-<cpu number>
+ The argument is a cpu list, as described above.
irqfixup [HW]
When an interrupt is not handled search all handlers
@@ -1812,13 +1837,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
Format: <RDP>,<reset>,<pci_scan>,<verbosity>
isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
- Format:
- <cpu number>,...,<cpu number>
- or
- <cpu number>-<cpu number>
- (must be a positive range in ascending order)
- or a mixture
- <cpu number>,...,<cpu number>-<cpu number>
+ The argument is a cpu list, as described above.
This option can be used to specify one or more CPUs
to isolate from the general SMP balancing and scheduling
@@ -2680,6 +2699,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
Default: on
nohz_full= [KNL,BOOT]
+ The argument is a cpu list, as described above.
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
@@ -3285,6 +3305,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
See Documentation/blockdev/ramdisk.txt.
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