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SubjectRe: [Patch Part3 v4 38/38] x86, irq: Add kernel parameter vector_alloc to set CPU vector allocation policy
On 12/01/2014 01:49 PM, Bjorn Helgaas wrote:
> On Tue, Nov 25, 2014 at 12:50 AM, Jiang Liu <jiang.liu@linux.intel.com> wrote:
>> 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.
>
> Why can't we figure this out automatically? Having a kernel parameter
> is a pain in the neck for users.

For the Numachip case, it would be sufficient to add a call to
set_vector_alloc_policy in the APIC driver, as this will always be
preferred for local MSI handling.

I'll follow up with a patch in the next day or so; further support for
other systems can be added later as and when tested.

>> Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
>> Cc: Daniel J Blueman <daniel@numascale.com>
>> ---
>> 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;
--
Daniel J Blueman
Principal Software Engineer, Numascale


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