From 51396556f0927c3d202f9903db5aa5aa8d4cbd2c Mon Sep 17 00:00:00 2001 From: Mike Christie Date: Mon, 4 Dec 2023 17:16:18 -0600 Subject: [PATCH] vhost-scsi: Add support for a worker thread per virtqueue This adds support for vhost-scsi to be able to create a worker thread per virtqueue. Right now for vhost-net we get a worker thread per tx/rx virtqueue pair which scales nicely as we add more virtqueues and CPUs, but for scsi we get the single worker thread that's shared by all virtqueues. When trying to send IO to more than 2 virtqueues the single thread becomes a bottlneck. This patch adds a new setting, worker_per_virtqueue, which can be set to: false: Existing behavior where we get the single worker thread. true: Create a worker per IO virtqueue. Signed-off-by: Mike Christie Reviewed-by: Stefan Hajnoczi Message-Id: <20231204231618.21962-3-michael.christie@oracle.com> Reviewed-by: Stefan Hajnoczi Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Stefano Garzarella --- hw/scsi/vhost-scsi.c | 62 +++++++++++++++++++++++++++++++++ include/hw/virtio/virtio-scsi.h | 1 + 2 files changed, 63 insertions(+) diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c index 3126df9e1d..08aa7534df 100644 --- a/hw/scsi/vhost-scsi.c +++ b/hw/scsi/vhost-scsi.c @@ -165,6 +165,59 @@ static const VMStateDescription vmstate_virtio_vhost_scsi = { .pre_save = vhost_scsi_pre_save, }; +static int vhost_scsi_set_workers(VHostSCSICommon *vsc, bool per_virtqueue) +{ + struct vhost_dev *dev = &vsc->dev; + struct vhost_vring_worker vq_worker; + struct vhost_worker_state worker; + int i, ret; + + /* Use default worker */ + if (!per_virtqueue || dev->nvqs == VHOST_SCSI_VQ_NUM_FIXED + 1) { + return 0; + } + + /* + * ctl/evt share the first worker since it will be rare for them + * to send cmds while IO is running. + */ + for (i = VHOST_SCSI_VQ_NUM_FIXED + 1; i < dev->nvqs; i++) { + memset(&worker, 0, sizeof(worker)); + + ret = dev->vhost_ops->vhost_new_worker(dev, &worker); + if (ret == -ENOTTY) { + /* + * worker ioctls are not implemented so just ignore and + * and continue device setup. + */ + warn_report("vhost-scsi: Backend supports a single worker. " + "Ignoring worker_per_virtqueue=true setting."); + ret = 0; + break; + } else if (ret) { + break; + } + + memset(&vq_worker, 0, sizeof(vq_worker)); + vq_worker.worker_id = worker.worker_id; + vq_worker.index = i; + + ret = dev->vhost_ops->vhost_attach_vring_worker(dev, &vq_worker); + if (ret == -ENOTTY) { + /* + * It's a bug for the kernel to have supported the worker creation + * ioctl but not attach. + */ + dev->vhost_ops->vhost_free_worker(dev, &worker); + break; + } else if (ret) { + break; + } + } + + return ret; +} + static void vhost_scsi_realize(DeviceState *dev, Error **errp) { VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(dev); @@ -232,6 +285,13 @@ static void vhost_scsi_realize(DeviceState *dev, Error **errp) goto free_vqs; } + ret = vhost_scsi_set_workers(vsc, vs->conf.worker_per_virtqueue); + if (ret < 0) { + error_setg(errp, "vhost-scsi: vhost worker setup failed: %s", + strerror(-ret)); + goto free_vqs; + } + /* At present, channel and lun both are 0 for bootable vhost-scsi disk */ vsc->channel = 0; vsc->lun = 0; @@ -297,6 +357,8 @@ static Property vhost_scsi_properties[] = { VIRTIO_SCSI_F_T10_PI, false), DEFINE_PROP_BOOL("migratable", VHostSCSICommon, migratable, false), + DEFINE_PROP_BOOL("worker_per_virtqueue", VirtIOSCSICommon, + conf.worker_per_virtqueue, false), DEFINE_PROP_END_OF_LIST(), }; diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h index 7f0573b1bf..7be0105918 100644 --- a/include/hw/virtio/virtio-scsi.h +++ b/include/hw/virtio/virtio-scsi.h @@ -51,6 +51,7 @@ typedef struct virtio_scsi_config VirtIOSCSIConfig; struct VirtIOSCSIConf { uint32_t num_queues; uint32_t virtqueue_size; + bool worker_per_virtqueue; bool seg_max_adjust; uint32_t max_sectors; uint32_t cmd_per_lun;