Re: [PATCH 0/3] irq/core: Fix and expand the irq affinity descriptor

[Sumit Saxena <sumit.saxena@broadcom.com>]

On Wed, Dec 19, 2018 at 4:23 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Tue, 4 Dec 2018, Dou Liyang wrote:
>
> > Now,  Spreading the interrupt affinity info by a cpumask pointer is not
> > enough, meets a problem[1] and hard to expand in the future.
> >
> > Fix it by:
> >
> >      +-----------------------------------+
> >      |                                   |
> >      |     struct cpumask *affinity      |
> >      |                                   |
> >      +-----------------------------------+
> >                        |
> >     +------------------v-------------------+
> >     |                                      |
> >     | struct irq_affinity_desc {           |
> >     |     struct cpumask   mask;           |
> >     |     unsigned int     is_managed : 1; |
> >     | };                                   |
> >     |                                      |
> >     +--------------------------------------+
> >
>
> So, I've applied that lot for 4.21 (or whatever number it will be). That's
> only the first step for solving Kashyap's problem.
>
> IIRC, then Kashap wanted to get initial interrupt spreading for these extra
> magic interrupts as well, but not have them marked managed.
>
> That's trivial to do now with the two queued changes in that area:
>
>   - The rework above
>
>   - The support for interrupt sets from Jens
>
> Just adding a small bitfield to struct irq_affinity which allows to tell
> the core that a particular interrupt set is not managed does the trick.
>
> Untested patch below.
>
> Kashyap, is that what you were looking for and if so, does it work?
Thomas,
We could not test these patches as they did net get applied to latest
linux-block tree cleanly.

Our requirement is: 1. extra interrupts should be un-managed and 2.
should be spread to CPUs of local NUMA node.
If interrupts are un-managed but not spread as per our requirement,
then still driver/userspace apps can manage by spreading
them as required by calling API- irq_set_affinity_hint().

Thanks,
Sumit
>
> Thanks,
>
>         tglx
>
> 8<-----------------
>
> Subject: genirq/affinity: Add support for non-managed affinity sets
> From: Thomas Gleixner <tglx@linutronix.de>
> Date: Tue, 18 Dec 2018 16:46:47 +0100
>
> Some drivers need an extra set of interrupts which are not marked managed,
> but should get initial interrupt spreading.
>
> Add a bitmap to struct irq_affinity which allows the driver to mark a
> particular set of interrupts as non managed. Check the bitmap during
> spreading and use the result to mark the interrupts in the sets
> accordingly.
>
> The unmanaged interrupts get initial spreading, but user space can change
> their affinity later on.
>
> Usage example:
>
>       struct irq_affinity affd = { .pre_vectors = 2 };
>       int sets[2];
>
>       /* Fill in sets[] */
>
>       affd.nr_sets = 2;
>       affd.sets = &sets;
>       affd.unmanaged_sets = 0x02;
>
>       ......
>
> So both sets are properly spread out, but the second set is not marked
> managed.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
>  include/linux/interrupt.h |   10 ++++++----
>  kernel/irq/affinity.c     |   24 ++++++++++++++----------
>  2 files changed, 20 insertions(+), 14 deletions(-)
>
> --- a/kernel/irq/affinity.c
> +++ b/kernel/irq/affinity.c
> @@ -99,7 +99,8 @@ static int __irq_build_affinity_masks(co
>                                       cpumask_var_t *node_to_cpumask,
>                                       const struct cpumask *cpu_mask,
>                                       struct cpumask *nmsk,
> -                                     struct irq_affinity_desc *masks)
> +                                     struct irq_affinity_desc *masks,
> +                                     bool managed)
>  {
>         int n, nodes, cpus_per_vec, extra_vecs, done = 0;
>         int last_affv = firstvec + numvecs;
> @@ -154,6 +155,7 @@ static int __irq_build_affinity_masks(co
>                         }
>                         irq_spread_init_one(&masks[curvec].mask, nmsk,
>                                                 cpus_per_vec);
> +                       masks[curvec].is_managed = managed;
>                 }
>
>                 done += v;
> @@ -176,7 +178,8 @@ static int __irq_build_affinity_masks(co
>  static int irq_build_affinity_masks(const struct irq_affinity *affd,
>                                     int startvec, int numvecs, int firstvec,
>                                     cpumask_var_t *node_to_cpumask,
> -                                   struct irq_affinity_desc *masks)
> +                                   struct irq_affinity_desc *masks,
> +                                   bool managed)
>  {
>         int curvec = startvec, nr_present, nr_others;
>         int ret = -ENOMEM;
> @@ -196,7 +199,8 @@ static int irq_build_affinity_masks(cons
>         /* Spread on present CPUs starting from affd->pre_vectors */
>         nr_present = __irq_build_affinity_masks(affd, curvec, numvecs,
>                                                 firstvec, node_to_cpumask,
> -                                               cpu_present_mask, nmsk, masks);
> +                                               cpu_present_mask, nmsk, masks,
> +                                               managed);
>
>         /*
>          * Spread on non present CPUs starting from the next vector to be
> @@ -211,7 +215,7 @@ static int irq_build_affinity_masks(cons
>         cpumask_andnot(npresmsk, cpu_possible_mask, cpu_present_mask);
>         nr_others = __irq_build_affinity_masks(affd, curvec, numvecs,
>                                                firstvec, node_to_cpumask,
> -                                              npresmsk, nmsk, masks);
> +                                              npresmsk, nmsk, masks, managed);
>         put_online_cpus();
>
>         if (nr_present < numvecs)
> @@ -268,10 +272,11 @@ irq_create_affinity_masks(int nvecs, con
>
>         for (i = 0, usedvecs = 0; i < nr_sets; i++) {
>                 int this_vecs = affd->sets ? affd->sets[i] : affvecs;
> +               bool managed = !test_bit(i, &affd->unmanaged_sets);
>                 int ret;
>
> -               ret = irq_build_affinity_masks(affd, curvec, this_vecs,
> -                                               curvec, node_to_cpumask, masks);
> +               ret = irq_build_affinity_masks(affd, curvec, this_vecs, curvec,
> +                                              node_to_cpumask, masks, managed);
>                 if (ret) {
>                         kfree(masks);
>                         masks = NULL;
> @@ -289,10 +294,6 @@ irq_create_affinity_masks(int nvecs, con
>         for (; curvec < nvecs; curvec++)
>                 cpumask_copy(&masks[curvec].mask, irq_default_affinity);
>
> -       /* Mark the managed interrupts */
> -       for (i = affd->pre_vectors; i < nvecs - affd->post_vectors; i++)
> -               masks[i].is_managed = 1;
> -
>  outnodemsk:
>         free_node_to_cpumask(node_to_cpumask);
>         return masks;
> @@ -316,6 +317,9 @@ int irq_calc_affinity_vectors(int minvec
>         if (affd->nr_sets) {
>                 int i;
>
> +               if (WARN_ON_ONCE(affd->nr_sets > BITS_PER_LONG))
> +                       return 0;
> +
>                 for (i = 0, set_vecs = 0;  i < affd->nr_sets; i++)
>                         set_vecs += affd->sets[i];
>         } else {
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -249,12 +249,14 @@ struct irq_affinity_notify {
>   *                     the MSI(-X) vector space
>   * @nr_sets:           Length of passed in *sets array
>   * @sets:              Number of affinitized sets
> + * @unmanaged_sets:    Bitmap to mark members of @sets as unmanaged
>   */
>  struct irq_affinity {
> -       int     pre_vectors;
> -       int     post_vectors;
> -       int     nr_sets;
> -       int     *sets;
> +       int             pre_vectors;
> +       int             post_vectors;
> +       int             nr_sets;
> +       int             *sets;
> +       unsigned long   unmanaged_sets;
>  };
>
>  /**