linux-kernel - [PATCH v5 5/9] virtio: blk/scsi: use block layer helpers to calculate num of queues

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Message-Id: <20250110-isolcpus-io-queues-v5-5-0e4f118680b0@kernel.org>
Date: Fri, 10 Jan 2025 17:26:43 +0100
From: Daniel Wagner <wagi@...nel.org>
To: Jens Axboe <axboe@...nel.dk>, Keith Busch <kbusch@...nel.org>, 
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, 
 "Michael S. Tsirkin" <mst@...hat.com>
Cc: "Martin K. Petersen" <martin.petersen@...cle.com>, 
 Thomas Gleixner <tglx@...utronix.de>, 
 Costa Shulyupin <costa.shul@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, 
 Valentin Schneider <vschneid@...hat.com>, Waiman Long <llong@...hat.com>, 
 Ming Lei <ming.lei@...hat.com>, Frederic Weisbecker <frederic@...nel.org>, 
 Mel Gorman <mgorman@...e.de>, Hannes Reinecke <hare@...e.de>, 
 linux-kernel@...r.kernel.org, linux-block@...r.kernel.org, 
 linux-nvme@...ts.infradead.org, megaraidlinux.pdl@...adcom.com, 
 linux-scsi@...r.kernel.org, storagedev@...rochip.com, 
 virtualization@...ts.linux.dev, GR-QLogic-Storage-Upstream@...vell.com, 
 Daniel Wagner <wagi@...nel.org>
Subject: [PATCH v5 5/9] virtio: blk/scsi: use block layer helpers to
 calculate num of queues

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.

Reviewed-by: Christoph Hellwig <hch@....de>
Acked-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Daniel Wagner <wagi@...nel.org>
---
 drivers/block/virtio_blk.c | 5 ++---
 drivers/scsi/virtio_scsi.c | 1 +
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 71a7ffeafb32ccd6329102d3166da7cbc8bc9539..c5b2ceebd645659d86299d07224d85bb7671a9a7 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/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