On Wed, Apr 10, 2024 at 11:30:20AM +0800, lyx634449800 wrote: > From: Yuxue Liu <yuxue.liu@xxxxxxxxxxxxxxx> > > When there is a ctlq and it doesn't require interrupt > callbacks,the original method of calculating vectors > wastes hardware msi or msix resources as well as system > IRQ resources. > > When conducting performance testing using testpmd in the > guest os, it was found that the performance was lower compared > to directly using vfio-pci to passthrough the device > > In scenarios where the virtio device in the guest os does > not utilize interrupts, the vdpa driver still configures > the hardware's msix vector. Therefore, the hardware still > sends interrupts to the host os. I just have a question on this part. How come hardware sends interrupts does not guest driver disable them? > Because of this unnecessary > action by the hardware, hardware performance decreases, and > it also affects the performance of the host os. > > Before modification:(interrupt mode) > 32: 0 0 0 0 PCI-MSI 32768-edge vp-vdpa[0000:00:02.0]-0 > 33: 0 0 0 0 PCI-MSI 32769-edge vp-vdpa[0000:00:02.0]-1 > 34: 0 0 0 0 PCI-MSI 32770-edge vp-vdpa[0000:00:02.0]-2 > 35: 0 0 0 0 PCI-MSI 32771-edge vp-vdpa[0000:00:02.0]-config > > After modification:(interrupt mode) > 32: 0 0 1 7 PCI-MSI 32768-edge vp-vdpa[0000:00:02.0]-0 > 33: 36 0 3 0 PCI-MSI 32769-edge vp-vdpa[0000:00:02.0]-1 > 34: 0 0 0 0 PCI-MSI 32770-edge vp-vdpa[0000:00:02.0]-config > > Before modification:(virtio pmd mode for guest os) > 32: 0 0 0 0 PCI-MSI 32768-edge vp-vdpa[0000:00:02.0]-0 > 33: 0 0 0 0 PCI-MSI 32769-edge vp-vdpa[0000:00:02.0]-1 > 34: 0 0 0 0 PCI-MSI 32770-edge vp-vdpa[0000:00:02.0]-2 > 35: 0 0 0 0 PCI-MSI 32771-edge vp-vdpa[0000:00:02.0]-config > > After modification:(virtio pmd mode for guest os) > 32: 0 0 0 0 PCI-MSI 32768-edge vp-vdpa[0000:00:02.0]-config > > To verify the use of the virtio PMD mode in the guest operating > system, the following patch needs to be applied to QEMU: > https://lore.kernel.org/all/20240408073311.2049-1-yuxue.liu@xxxxxxxxxxxxxxx > > Signed-off-by: Yuxue Liu <yuxue.liu@xxxxxxxxxxxxxxx> > Acked-by: Jason Wang <jasowang@xxxxxxxxxx> > Reviewed-by: Heng Qi <hengqi@xxxxxxxxxxxxxxxxx> > --- > V5: modify the description of the printout when an exception occurs > V4: update the title and assign values to uninitialized variables > V3: delete unused variables and add validation records > V2: fix when allocating IRQs, scan all queues > > drivers/vdpa/virtio_pci/vp_vdpa.c | 22 ++++++++++++++++------ > 1 file changed, 16 insertions(+), 6 deletions(-) > > diff --git a/drivers/vdpa/virtio_pci/vp_vdpa.c b/drivers/vdpa/virtio_pci/vp_vdpa.c > index df5f4a3bccb5..8de0224e9ec2 100644 > --- a/drivers/vdpa/virtio_pci/vp_vdpa.c > +++ b/drivers/vdpa/virtio_pci/vp_vdpa.c > @@ -160,7 +160,13 @@ static int vp_vdpa_request_irq(struct vp_vdpa *vp_vdpa) > struct pci_dev *pdev = mdev->pci_dev; > int i, ret, irq; > int queues = vp_vdpa->queues; > - int vectors = queues + 1; > + int vectors = 1; > + int msix_vec = 0; > + > + for (i = 0; i < queues; i++) { > + if (vp_vdpa->vring[i].cb.callback) > + vectors++; > + } > > ret = pci_alloc_irq_vectors(pdev, vectors, vectors, PCI_IRQ_MSIX); > if (ret != vectors) { > @@ -173,9 +179,12 @@ static int vp_vdpa_request_irq(struct vp_vdpa *vp_vdpa) > vp_vdpa->vectors = vectors; > > for (i = 0; i < queues; i++) { > + if (!vp_vdpa->vring[i].cb.callback) > + continue; > + > snprintf(vp_vdpa->vring[i].msix_name, VP_VDPA_NAME_SIZE, > "vp-vdpa[%s]-%d\n", pci_name(pdev), i); > - irq = pci_irq_vector(pdev, i); > + irq = pci_irq_vector(pdev, msix_vec); > ret = devm_request_irq(&pdev->dev, irq, > vp_vdpa_vq_handler, > 0, vp_vdpa->vring[i].msix_name, > @@ -185,21 +194,22 @@ static int vp_vdpa_request_irq(struct vp_vdpa *vp_vdpa) > "vp_vdpa: fail to request irq for vq %d\n", i); > goto err; > } > - vp_modern_queue_vector(mdev, i, i); > + vp_modern_queue_vector(mdev, i, msix_vec); > vp_vdpa->vring[i].irq = irq; > + msix_vec++; > } > > snprintf(vp_vdpa->msix_name, VP_VDPA_NAME_SIZE, "vp-vdpa[%s]-config\n", > pci_name(pdev)); > - irq = pci_irq_vector(pdev, queues); > + irq = pci_irq_vector(pdev, msix_vec); > ret = devm_request_irq(&pdev->dev, irq, vp_vdpa_config_handler, 0, > vp_vdpa->msix_name, vp_vdpa); > if (ret) { > dev_err(&pdev->dev, > - "vp_vdpa: fail to request irq for vq %d\n", i); > + "vp_vdpa: fail to request irq for config: %d\n", ret); > goto err; > } > - vp_modern_config_vector(mdev, queues); > + vp_modern_config_vector(mdev, msix_vec); > vp_vdpa->config_irq = irq; > > return 0; > -- > 2.43.0
