From: Jonathan Lim <jolim@redhat.com> Date: Thu, 11 Oct 2007 15:19:21 -0400 Subject: [misc] Allow a hyphenated range for isolcpus Message-id: 20071011191921.GE5008@sgi-desktop.boston.redhat.com O-Subject: [RHEL5.2 PATCH] BZ 328151: Allow a hyphenated range for isolcpus Bugzilla: 328151 Currently, the command line option "isolcpus=" takes as its argument a list of cpus. This can get extremely long when isolating the majority of cpus on a large system. This patch allows a hyphenated range of positive numbers in the string passed to command line helper function, get_options. The kernel isolcpus code would not need any changing to use this feature. The patch has been tested on x86_64 and is upstream: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=22f2e280179946b8be1e2205b8654f2cb4abbf64 Following is the diff against the 2.6.18-52.el5 kernel source: Acked-by: Prarit Bhargava <prarit@redhat.com> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 1e20a69..4f239be 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -727,7 +727,12 @@ running once the system is up. Format: <RDP>,<reset>,<pci_scan>,<verbosity> isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. - Format: <cpu number>,...,<cpu number> + 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> This option can be used to specify one or more CPUs to isolate from the general SMP balancing and scheduling algorithms. The only way to move a process onto or off diff --git a/lib/cmdline.c b/lib/cmdline.c index 0331ed8..8a5b530 100644 --- a/lib/cmdline.c +++ b/lib/cmdline.c @@ -16,6 +16,23 @@ #include <linux/kernel.h> #include <linux/string.h> +/* + * If a hyphen was found in get_option, this will handle the + * range of numbers, M-N. This will expand the range and insert + * the values[M, M+1, ..., N] into the ints array in get_options. + */ + +static int get_range(char **str, int *pint) +{ + int x, inc_counter, upper_range; + + (*str)++; + upper_range = simple_strtol((*str), NULL, 0); + inc_counter = upper_range - *pint; + for (x = *pint; x < upper_range; x++) + *pint++ = x; + return inc_counter; +} /** * get_option - Parse integer from an option string @@ -29,6 +46,7 @@ * 0 : no int in string * 1 : int found, no subsequent comma * 2 : int found including a subsequent comma + * 3 : hyphen found to denote a range */ int get_option (char **str, int *pint) @@ -44,6 +62,8 @@ int get_option (char **str, int *pint) (*str)++; return 2; } + if (**str == '-') + return 3; return 1; } @@ -55,7 +75,8 @@ int get_option (char **str, int *pint) * @ints: integer array * * This function parses a string containing a comma-separated - * list of integers. The parse halts when the array is + * list of integers, a hyphen-separated range of _positive_ integers, + * or a combination of both. The parse halts when the array is * full, or when no more numbers can be retrieved from the * string. * @@ -72,6 +93,18 @@ char *get_options(const char *str, int nints, int *ints) res = get_option ((char **)&str, ints + i); if (res == 0) break; + if (res == 3) { + int range_nums; + range_nums = get_range((char **)&str, ints + i); + if (range_nums < 0) + break; + /* + * Decrement the result by one to leave out the + * last number in the range. The next iteration + * will handle the upper number in the range + */ + i += (range_nums - 1); + } i++; if (res == 1) break;