| Message ID | 20240408060842.2012-1-yuxue.liu@jaguarmicro.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | vhost: don't set vring call if no enabled msix | expand |
On Mon, Apr 8, 2024 at 2:09 PM lyx634449800 <yuxue.liu@jaguarmicro.com> wrote: > > When conducting performance testing using testpmd in the guest os, > it was observed that the performance was lower compared to the > scenario of direct vfio-pci usage. > > In the virtual machine operating system, even if the virtio device > does not use msix interrupts, vhost still sets vring call fd. This > leads to unnecessary performance overhead. If the guest driver does > not enable msix capability (e.g virtio-net pmd), we should also > check and clear the vring call fd. > > Signed-off-by: Yuxue Liu <yuxue.liu@jaguarmicro.com> Patch looks good, I would like to do the following tweaks: 1) explain what is not enough since commit: commit 96a3d98d2cdbd897ff5ab33427aa4cfb94077665 Author: Jason Wang <jasowang@redhat.com> Date: Mon Aug 1 16:07:58 2016 +0800 vhost: don't set vring call if no vector 2) tweak the title to "vhost: don't set vring call if guest notifiers is not enabled" as it's not necessarily pci but also ccw. Thanks > --- > hw/virtio/vhost.c | 16 +++++++++------- > 1 file changed, 9 insertions(+), 7 deletions(-) > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > index f50180e60e..b972c84e67 100644 > --- a/hw/virtio/vhost.c > +++ b/hw/virtio/vhost.c > @@ -1266,13 +1266,15 @@ int vhost_virtqueue_start(struct vhost_dev *dev, > vhost_virtqueue_mask(dev, vdev, idx, false); > } > > - if (k->query_guest_notifiers && > - k->query_guest_notifiers(qbus->parent) && > - virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR) { > - file.fd = -1; > - r = dev->vhost_ops->vhost_set_vring_call(dev, &file); > - if (r) { > - goto fail_vector; > + if (k->query_guest_notifiers) { > + if (!k->query_guest_notifiers(qbus->parent) || > + (k->query_guest_notifiers(qbus->parent) && > + virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR)) { > + file.fd = -1; > + r = dev->vhost_ops->vhost_set_vring_call(dev, &file); > + if (r) { > + goto fail_vector; > + } > } > } > > -- > 2.43.0 >
On Mon, Apr 08, 2024 at 02:08:42PM +0800, lyx634449800 wrote: > When conducting performance testing using testpmd in the guest os, > it was observed that the performance was lower compared to the > scenario of direct vfio-pci usage. > > In the virtual machine operating system, even if the virtio device > does not use msix interrupts, vhost still sets vring call fd. This > leads to unnecessary performance overhead. If the guest driver does > not enable msix capability (e.g virtio-net pmd), we should also > check and clear the vring call fd. > > Signed-off-by: Yuxue Liu <yuxue.liu@jaguarmicro.com> Fails testing under cross-i686-tci: https://gitlab.com/mstredhat/qemu/-/jobs/6578881990 36/258 qemu:qtest+qtest-i386 / qtest-i386/ioh3420-test OK 0.15s 1 subtests passed ▶ 37/258 ERROR:../tests/qtest/qos-test.c:191:subprocess_run_one_test: child process (/aarch64/virt/generic-pcihost/pci-bus-generic/pci-bus/virtio-net-pci/virtio-net/virtio-net-tests/vhost-user/migrate/subprocess [22197]) failed unexpectedly ERROR 38/258 qemu:qtest+qtest-i386 / qtest-i386/lpc-ich9-test OK 0.16s 1 subtests passed 37/258 qemu:qtest+qtest-aarch64 / qtest-aarch64/qos-test ERROR 13.20s killed by signal 6 SIGABRT >>> G_TEST_DBUS_DAEMON=/builds/mstredhat/qemu/tests/dbus-vmstate-daemon.sh PYTHON=/builds/mstredhat/qemu/build/pyvenv/bin/python3 MALLOC_PERTURB_=144 QTEST_QEMU_BINARY=./qemu-system-aarch64 /builds/mstredhat/qemu/build/tests/qtest/qos-test --tap -k ――――――――――――――――――――――――――――――――――――― ✀ ――――――――――――――――――――――――――――――――――――― stderr: ** ERROR:../tests/qtest/vhost-user-test.c:468:chr_read: assertion failed (err == NULL): Bad file descriptor (g-unix-error-quark, 0) ** ERROR:../tests/qtest/qos-test.c:191:subprocess_run_one_test: child process (/aarch64/virt/generic-pcihost/pci-bus-generic/pci-bus/virtio-net-pci/virtio-net/virtio-net-tests/vhost-user/migrate/subprocess [22197]) failed unexpectedly (test program exited with status code -6) ―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――― > --- > hw/virtio/vhost.c | 16 +++++++++------- > 1 file changed, 9 insertions(+), 7 deletions(-) > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > index f50180e60e..b972c84e67 100644 > --- a/hw/virtio/vhost.c > +++ b/hw/virtio/vhost.c > @@ -1266,13 +1266,15 @@ int vhost_virtqueue_start(struct vhost_dev *dev, > vhost_virtqueue_mask(dev, vdev, idx, false); > } > > - if (k->query_guest_notifiers && > - k->query_guest_notifiers(qbus->parent) && > - virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR) { > - file.fd = -1; > - r = dev->vhost_ops->vhost_set_vring_call(dev, &file); > - if (r) { > - goto fail_vector; > + if (k->query_guest_notifiers) { > + if (!k->query_guest_notifiers(qbus->parent) || > + (k->query_guest_notifiers(qbus->parent) && > + virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR)) { > + file.fd = -1; > + r = dev->vhost_ops->vhost_set_vring_call(dev, &file); > + if (r) { > + goto fail_vector; > + } > } > } > > -- > 2.43.0
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index f50180e60e..b972c84e67 100644 --- a/hw/virtio/vhost.c +++ b/hw/virtio/vhost.c @@ -1266,13 +1266,15 @@ int vhost_virtqueue_start(struct vhost_dev *dev, vhost_virtqueue_mask(dev, vdev, idx, false); } - if (k->query_guest_notifiers && - k->query_guest_notifiers(qbus->parent) && - virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR) { - file.fd = -1; - r = dev->vhost_ops->vhost_set_vring_call(dev, &file); - if (r) { - goto fail_vector; + if (k->query_guest_notifiers) { + if (!k->query_guest_notifiers(qbus->parent) || + (k->query_guest_notifiers(qbus->parent) && + virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR)) { + file.fd = -1; + r = dev->vhost_ops->vhost_set_vring_call(dev, &file); + if (r) { + goto fail_vector; + } } }
When conducting performance testing using testpmd in the guest os, it was observed that the performance was lower compared to the scenario of direct vfio-pci usage. In the virtual machine operating system, even if the virtio device does not use msix interrupts, vhost still sets vring call fd. This leads to unnecessary performance overhead. If the guest driver does not enable msix capability (e.g virtio-net pmd), we should also check and clear the vring call fd. Signed-off-by: Yuxue Liu <yuxue.liu@jaguarmicro.com> --- hw/virtio/vhost.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)