Re: [PATCH v4 6/9] virtio: blk/scsi: use block layer helpers to calculate num of queues

Michael S. Tsirkin
2024-12-19T15:57:15Z

On Tue, Dec 17, 2024 at 07:29:40PM +0100, Daniel Wagner wrote:
> Multiqueue devices should only allocate queues for the housekeeping CPUs
> when isolcpus=managed_irq is set. This avoids that the isolated CPUs get
> disturbed with OS workload.
>
> Use helpers which calculates the correct number of queues which should
> be used when isolcpus is used.
>
> Signed-off-by: Daniel Wagner <wagi@kernel.org>

The subject is misleading, one thinks it is onlu virtio blk.
It's best to just split each driver in a patch by its own.
for the changes in virtio:

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
> drivers/block/virtio_blk.c | 5 ++---
> drivers/scsi/megaraid/megaraid_sas_base.c | 3 ++-
> drivers/scsi/virtio_scsi.c | 1 +
> 3 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index ed514ff46dc82acd629ae594cb0fa097bd301a9b..0287ceaaf19972f3a18e81cd2e3252e4d539ba93 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -976,9 +976,8 @@ static int init_vq(struct virtio_blk *vblk)
> return -EINVAL;
> }
>
> - num_vqs = min_t(unsigned int,
> - min_not_zero(num_request_queues, nr_cpu_ids),
> - num_vqs);
> + num_vqs = blk_mq_num_possible_queues(
> + min_not_zero(num_request_queues, num_vqs));
>
> num_poll_vqs = min_t(unsigned int, poll_queues, num_vqs - 1);
>
> diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c b/drivers/scsi/megaraid/megaraid_sas_base.c
> index 59d385e5a917979ae2f61f5db2c3355b9cab7e08..3ff0978b3acb5baf757fee25d9fccf4971976272 100644
> --- a/drivers/scsi/megaraid/megaraid_sas_base.c
> +++ b/drivers/scsi/megaraid/megaraid_sas_base.c
> @@ -6236,7 +6236,8 @@ static int megasas_init_fw(struct megasas_instance *instance)
> intr_coalescing = (scratch_pad_1 & MR_INTR_COALESCING_SUPPORT_OFFSET) ?
> true : false;
> if (intr_coalescing &&
> - (blk_mq_num_online_queues(0) >= MR_HIGH_IOPS_QUEUE_COUNT) &&
> + (blk_mq_num_online_queues(0) >=
> + MR_HIGH_IOPS_QUEUE_COUNT) &&
> (instance->msix_vectors == MEGASAS_MAX_MSIX_QUEUES))
> instance->perf_mode = MR_BALANCED_PERF_MODE;
> else
> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
> index 60be1a0c61836ba643adcf9ad8d5b68563a86cb1..46ca0b82f57ce2211c7e2817dd40ee34e65bcbf9 100644
> --- a/drivers/scsi/virtio_scsi.c
> +++ b/drivers/scsi/virtio_scsi.c
> @@ -919,6 +919,7 @@ static int virtscsi_probe(struct virtio_device *vdev)
> /* We need to know how many queues before we allocate. */
> num_queues = virtscsi_config_get(vdev, num_queues) ? : 1;
> num_queues = min_t(unsigned int, nr_cpu_ids, num_queues);
> + num_queues = blk_mq_num_possible_queues(num_queues);
>
> num_targets = virtscsi_config_get(vdev, max_target) + 1;
>
>
> --
> 2.47.1