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

[Bjorn Helgaas]

On Mon, Dec 1, 2014 at 4:45 PM, Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx> wrote:
>
>
> On 2014/12/2 2:49, Bjorn Helgaas wrote:
>> On Tue, Nov 25, 2014 at 12:50 AM, Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx> 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.
> Hi Bjorn,
>         I'm thinking of automatically turning on local vector
> allocation if any host bridge has an assigned(valid) NUMA node id.
> By this way, user doesn't need to specify the kernel parameter for most
> cases. How about this solution?

I'm not an IRQ person, but your idea sounds like figuring this out
automatically, and I'm in favor of that :)

>>> 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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