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

[Daniel J Blueman]

On 12/01/2014 01:49 PM, 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.

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@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;
--
Daniel J Blueman
Principal Software Engineer, Numascale
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/