[Patch Part3 v4 38/38] x86, irq: Add kernel parameter vector_alloc to set CPU vector allocation policy

[Jiang Liu]

Parameter vector_alloc should be set to an integer with:
bit 0:	enable allocating CPU vector from CPUs on device local node.
	That's to allocate from cpumask_of_node(irq_data->node).
bit 1: enable the default policy, which is to allocate from
       apic->target_cpus().

When allocating vectors, it tries all enabled policies from lower bit
position to higher bit position.

This option could be use to optimize interrupt distribution on large
system such as NumaChip etc.

Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
Cc: Daniel J Blueman <daniel@xxxxxxxxxxxxx>
---
 Documentation/kernel-parameters.txt |    6 ++++++
 arch/x86/kernel/apic/vector.c       |   11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4c81a860cc2b..a175c5016954 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3709,6 +3709,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	vector=		[IA-64,SMP]
 			vector=percpu: enable percpu vector domain
 
+	vector_alloc=	[x86,SMP]
+			vector_alloc=policy: policy is a bitmap, bit 0
+			for allocating CPU vector from CPUs on device local
+			node; bit 1 for the default policy to allocating from
+			apic->target_cpus(). All higher bits are reserved.
+
 	video=		[FB] Frame buffer configuration
 			See Documentation/fb/modedb.txt.
 
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index 16de8906ee1e..1158843551c7 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -79,6 +79,17 @@ void set_vector_alloc_policy(unsigned int policy)
 		x86_vector_alloc_policy = policy | X86_VECTOR_POL_CALLER;
 }
 
+static int __init apic_parse_vector_policy(char *str)
+{
+	int policy;
+
+	if (get_option(&str, &policy) == 1)
+		set_vector_alloc_policy(policy);
+
+	return 1;
+}
+__setup("vector_alloc=", apic_parse_vector_policy);
+
 static struct apic_chip_data *alloc_apic_chip_data(int node)
 {
 	struct apic_chip_data *data;
-- 
1.7.10.4

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