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Message-ID: <4944B5A4.9060706@kernel.org>
Date: Sat, 13 Dec 2008 23:28:36 -0800
From: Yinghai Lu <yinghai@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] add init_start_cpus to config boot cpus -v2
Impact: new command line
so could select cpus to be started during init stage.
example:
init_start_cpus=2,4,6
to start core 0 only on every node or thread 0 or all cores
init_start_cpus=0
not start other APs, and later let user to use
echo 1 > /sys/devices/cpu/cpu2
to start them in user space.
Signed-off-by: Yinghai Lu <yinghai@...nel.org>
---
Documentation/kernel-parameters.txt | 14 ++++++++++++++
init/main.c | 19 ++++++++++++++++++-
2 files changed, 32 insertions(+), 1 deletion(-)
Index: linux-2.6/Documentation/kernel-parameters.txt
===================================================================
--- linux-2.6.orig/Documentation/kernel-parameters.txt
+++ linux-2.6/Documentation/kernel-parameters.txt
@@ -918,6 +918,20 @@ and is between 256 and 4096 characters.
forcesac
soft
+ init_start_cpus= [KNL,SMP] set CPUs that will be started during
+ init stage.
+ 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 be started during init stage.
+ <cpu number> begins at 0 and the maximum value is
+ "number of CPUs in system - 1".
intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
off
Index: linux-2.6/init/main.c
===================================================================
--- linux-2.6.orig/init/main.c
+++ linux-2.6/init/main.c
@@ -413,11 +413,28 @@ static void __init setup_per_cpu_areas(v
}
#endif /* CONFIG_HAVE_SETUP_PER_CPU_AREA */
+static __initdata cpumask_var_t cpu_init_start_mask;
+
+/* Setup the mask of cpus configured for init start */
+static int __init init_start_cpu_setup(char *str)
+{
+ cpulist_parse(str, *cpu_init_start_mask);
+
+ return 1;
+}
+
+__setup("init_start_cpus=", init_start_cpu_setup);
+
/* Called by boot processor to activate the rest. */
static void __init smp_init(void)
{
unsigned int cpu;
+ if (cpumask_empty(cpu_init_start_mask))
+ cpumask_copy(cpu_init_start_mask, &cpu_present_map);
+ else
+ cpumask_and(cpu_init_start_mask, cpu_init_start_mask,
+ &cpu_present_map);
/*
* Set up the current CPU as possible to migrate to.
* The other ones will be done by cpu_up/cpu_down()
@@ -426,7 +443,7 @@ static void __init smp_init(void)
cpu_set(cpu, cpu_active_map);
/* FIXME: This should be done in userspace --RR */
- for_each_present_cpu(cpu) {
+ for_each_cpu_mask_nr(cpu, *cpu_init_start_mask) {
if (num_online_cpus() >= setup_max_cpus)
break;
if (!cpu_online(cpu))
--
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