better subject: vp_vdpa: don't allocate unused msix vectors to make it clear it's not a bugfix. more comments below, but most importantly this looks like it adds a bug. On Tue, Apr 09, 2024 at 09:49:35AM +0800, lyx634449800 wrote: > 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. 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: lyx634449800 <yuxue.liu@xxxxxxxxxxxxxxx> Bad S.O.B format. Should be Signed-off-by: Real Name <email> > --- > > V3: delete unused variables and add validation records > V2: fix when allocating IRQs, scan all queues > > drivers/vdpa/virtio_pci/vp_vdpa.c | 35 +++++++++++++++++++------------ > 1 file changed, 22 insertions(+), 13 deletions(-) > > diff --git a/drivers/vdpa/virtio_pci/vp_vdpa.c b/drivers/vdpa/virtio_pci/vp_vdpa.c > index df5f4a3bccb5..cd3aeb3b8f21 100644 > --- a/drivers/vdpa/virtio_pci/vp_vdpa.c > +++ b/drivers/vdpa/virtio_pci/vp_vdpa.c > @@ -160,22 +160,31 @@ 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 msix_vec, allocated_vectors = 0; I would actually call allocated_vectors -> vectors, make the patch smaller. > > - ret = pci_alloc_irq_vectors(pdev, vectors, vectors, PCI_IRQ_MSIX); > - if (ret != vectors) { > + for (i = 0; i < queues; i++) { > + if (vp_vdpa->vring[i].cb.callback) > + allocated_vectors++; > + } > + allocated_vectors = allocated_vectors + 1; better: allocated_vectors++; /* extra one for config */ > + > + ret = pci_alloc_irq_vectors(pdev, allocated_vectors, allocated_vectors, > + PCI_IRQ_MSIX); > + if (ret != allocated_vectors) { > dev_err(&pdev->dev, > "vp_vdpa: fail to allocate irq vectors want %d but %d\n", > - vectors, ret); > + allocated_vectors, ret); > return ret; > } > - > - vp_vdpa->vectors = vectors; > + vp_vdpa->vectors = allocated_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); using uninitialized msix_vec here? I would expect compiler to warn about it. pay attention to compiler warnings pls. > ret = devm_request_irq(&pdev->dev, irq, > vp_vdpa_vq_handler, > 0, vp_vdpa->vring[i].msix_name, > @@ -185,23 +194,23 @@ 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); > + pci_name(pdev)); don't move pci_name - don't make unrelated code changes. > + 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\n"); I would report ret here too. > goto err; > } > - vp_modern_config_vector(mdev, queues); > + vp_modern_config_vector(mdev, msix_vec); > vp_vdpa->config_irq = irq; > - don't make unrelated code changes. > return 0; > err: > vp_vdpa_free_irq(vp_vdpa); > -- > 2.43.0
