Hi Thomas,
On Sat, Feb 16, 2019 at 06:13:13PM +0100, Thomas Gleixner wrote:
> Some drivers need an extra set of interrupts which should not be marked
> managed, but should get initial interrupt spreading.
Could you share the drivers and their use case?
>
> 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. For the managed sets, i.e. the corresponding bit
> in the mask is not set, there is no change in behaviour.
>
> Usage example:
>
> struct irq_affinity affd = {
> .pre_vectors = 2,
> .unmanaged_sets = 0x02,
> .calc_sets = drv_calc_sets,
> };
> ....
>
> For both interrupt sets the interrupts are properly spread out, but the
> second set is not marked managed.
Given drivers only care the managed vs non-managed interrupt numbers,
just wondering why this case can't be covered by .pre_vectors &
.post_vectors?
Also this kind of usage may break blk-mq easily, in which the following
rule needs to be respected:
1) all CPUs are required to spread among each interrupt set
2) no any CPU is shared between two IRQs in same set.
>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> ---
> include/linux/interrupt.h | 2 ++
> kernel/irq/affinity.c | 16 +++++++++++-----
> 2 files changed, 13 insertions(+), 5 deletions(-)
>
> Index: b/include/linux/interrupt.h
> ===================================================================
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -251,6 +251,7 @@ struct irq_affinity_notify {
> * the MSI(-X) vector space
> * @nr_sets: The number of interrupt sets for which affinity
> * spreading is required
> + * @unmanaged_sets: Bitmap to mark entries in the @set_size array unmanaged
> * @set_size: Array holding the size of each interrupt set
> * @calc_sets: Callback for calculating the number and size
> * of interrupt sets
> @@ -261,6 +262,7 @@ struct irq_affinity {
> unsigned int pre_vectors;
> unsigned int post_vectors;
> unsigned int nr_sets;
> + unsigned int unmanaged_sets;
> unsigned int set_size[IRQ_AFFINITY_MAX_SETS];
> void (*calc_sets)(struct irq_affinity *, unsigned int nvecs);
> void *priv;
> Index: b/kernel/irq/affinity.c
> ===================================================================
> --- a/kernel/irq/affinity.c
> +++ b/kernel/irq/affinity.c
> @@ -249,6 +249,8 @@ irq_create_affinity_masks(unsigned int n
> unsigned int affvecs, curvec, usedvecs, i;
> struct irq_affinity_desc *masks = NULL;
>
> + BUILD_BUG_ON(IRQ_AFFINITY_MAX_SETS > sizeof(affd->unmanaged_sets) * 8);
> +
> /*
> * Determine the number of vectors which need interrupt affinities
> * assigned. If the pre/post request exhausts the available vectors
> @@ -292,7 +294,8 @@ irq_create_affinity_masks(unsigned int n
> * have multiple sets, build each sets affinity mask separately.
> */
> for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) {
> - unsigned int this_vecs = affd->set_size[i];
> + bool managed = affd->unmanaged_sets & (1U << i) ? true : false;
The above check is inverted.
Thanks,
Ming
