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-rw-r--r--Documentation/kernel-parameters.txt50
-rw-r--r--lib/bitmap.c50
2 files changed, 82 insertions, 18 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
diff --git a/lib/bitmap.c b/lib/bitmap.c
index eca88087fa8a..0b66f0e5eb6b 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -496,6 +496,11 @@ EXPORT_SYMBOL(bitmap_print_to_pagebuf);
* ranges. Consecutively set bits are shown as two hyphen-separated
* decimal numbers, the smallest and largest bit numbers set in
* the range.
+ * Optionally each range can be postfixed to denote that only parts of it
+ * should be set. The range will divided to groups of specific size.
+ * From each group will be used only defined amount of bits.
+ * Syntax: range:used_size/group_size
+ * Example: 0-1023:2/256 ==> 0,1,256,257,512,513,768,769
*
* Returns 0 on success, -errno on invalid input strings.
* Error values:
@@ -507,16 +512,20 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
int is_user, unsigned long *maskp,
int nmaskbits)
{
- unsigned a, b;
+ unsigned int a, b, old_a, old_b;
+ unsigned int group_size, used_size;
int c, old_c, totaldigits, ndigits;
const char __user __force *ubuf = (const char __user __force *)buf;
- int at_start, in_range;
+ int at_start, in_range, in_partial_range;
totaldigits = c = 0;
+ old_a = old_b = 0;
+ group_size = used_size = 0;
bitmap_zero(maskp, nmaskbits);
do {
at_start = 1;
in_range = 0;
+ in_partial_range = 0;
a = b = 0;
ndigits = totaldigits;
@@ -547,6 +556,24 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
if ((totaldigits != ndigits) && isspace(old_c))
return -EINVAL;
+ if (c == '/') {
+ used_size = a;
+ at_start = 1;
+ in_range = 0;
+ a = b = 0;
+ continue;
+ }
+
+ if (c == ':') {
+ old_a = a;
+ old_b = b;
+ at_start = 1;
+ in_range = 0;
+ in_partial_range = 1;
+ a = b = 0;
+ continue;
+ }
+
if (c == '-') {
if (at_start || in_range)
return -EINVAL;
@@ -567,15 +594,30 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
}
if (ndigits == totaldigits)
continue;
+ if (in_partial_range) {
+ group_size = a;
+ a = old_a;
+ b = old_b;
+ old_a = old_b = 0;
+ }
/* if no digit is after '-', it's wrong*/
if (at_start && in_range)
return -EINVAL;
- if (!(a <= b))
+ if (!(a <= b) || !(used_size <= group_size))
return -EINVAL;
if (b >= nmaskbits)
return -ERANGE;
while (a <= b) {
- set_bit(a, maskp);
+ if (in_partial_range) {
+ static int pos_in_group = 1;
+
+ if (pos_in_group <= used_size)
+ set_bit(a, maskp);
+
+ if (a == b || ++pos_in_group > group_size)
+ pos_in_group = 1;
+ } else
+ set_bit(a, maskp);
a++;
}
} while (buflen && c == ',');