On Tue, 31 May 2016 12:43:11 +0800
Jason Wang <jasow...@redhat.com> wrote:
> On 2016年05月31日 12:19, Michael S. Tsirkin wrote:
> > On Tue, May 31, 2016 at 11:04:18AM +0800, Jason Wang wrote:
> >>
> >> On 2016年05月31日 02:07, Michael S. Tsirkin wrote:
> >>> On Thu, Apr 07, 2016 at 12:56:24PM +0800, Jason Wang wrote:
> >>>> This patch add the capability of basic vhost net busy polling which is
> >>>> supported by recent kernel. User could configure the maximum number of
> >>>> us that could be spent on busy polling through a new property of tap
> >>>> "vhost-poll-us".
> >>> I applied this but now I had a thought - should we generalize this to
> >>> "poll-us"? Down the road tun could support busy olling just like
> >>> sockets do.
> >> Looks two different things. Socket busy polling depends on the value set by
> >> sysctl or SO_BUSY_POLL, which should be transparent to qemu.
> > This is what I am saying. qemu can set SO_BUSY_POLL if poll-us is
> > specified,
> > can it not?
>
> With CAP_NET_ADMIN, it can. Without it, it can only decrease the value.
>
> > Onthe one hand this suggests a more generic name
> > for the option.
>
> I see, but there're some differences:
>
> - socket busy polling only poll for rx, vhost busy polling poll for both
> tx and rx.
> - vhost busy polling does not depends on socket busy polling, it can
> work with socket busy polling disabled.
>
FWIW since these are different things, maybe the user would want to use
both (?)... in which case a single API could be painful.
> > On the other how does user discover whether it's
> > implemented for tap without vhost? Do we require kernel support?
>
> I believe this could be done by management through ioctl probing.
>
> > Does an unblocking read with tap without vhost also speed
> > things up a bit?
>
> Kernel will try one more round of napi poll, so we can only get speed up
> if we can poll some packet in this case.
>
> >
> >>>> Signed-off-by: Jason Wang <jasow...@redhat.com>
> >>>> ---
> >>>> hw/net/vhost_net.c | 2 +-
> >>>> hw/scsi/vhost-scsi.c | 2 +-
> >>>> hw/virtio/vhost-backend.c | 8 ++++++++
> >>>> hw/virtio/vhost.c | 40
> >>>> ++++++++++++++++++++++++++++++++++++++-
> >>>> include/hw/virtio/vhost-backend.h | 3 +++
> >>>> include/hw/virtio/vhost.h | 3 ++-
> >>>> include/net/vhost_net.h | 1 +
> >>>> net/tap.c | 10 ++++++++--
> >>>> net/vhost-user.c | 1 +
> >>>> qapi-schema.json | 6 +++++-
> >>>> qemu-options.hx | 3 +++
> >>>> 11 files changed, 72 insertions(+), 7 deletions(-)
> >>>>
> >>>> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> >>>> index 6e1032f..1840c73 100644
> >>>> --- a/hw/net/vhost_net.c
> >>>> +++ b/hw/net/vhost_net.c
> >>>> @@ -166,7 +166,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions
> >>>> *options)
> >>>> }
> >>>> r = vhost_dev_init(&net->dev, options->opaque,
> >>>> - options->backend_type);
> >>>> + options->backend_type,
> >>>> options->busyloop_timeout);
> >>>> if (r < 0) {
> >>>> goto fail;
> >>>> }
> >>>> diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
> >>>> index 9261d51..2a00f2f 100644
> >>>> --- a/hw/scsi/vhost-scsi.c
> >>>> +++ b/hw/scsi/vhost-scsi.c
> >>>> @@ -248,7 +248,7 @@ static void vhost_scsi_realize(DeviceState *dev,
> >>>> Error **errp)
> >>>> s->dev.backend_features = 0;
> >>>> ret = vhost_dev_init(&s->dev, (void *)(uintptr_t)vhostfd,
> >>>> - VHOST_BACKEND_TYPE_KERNEL);
> >>>> + VHOST_BACKEND_TYPE_KERNEL, 0);
> >>>> if (ret < 0) {
> >>>> error_setg(errp, "vhost-scsi: vhost initialization failed: %s",
> >>>> strerror(-ret));
> >>>> diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> >>>> index b358902..d62372e 100644
> >>>> --- a/hw/virtio/vhost-backend.c
> >>>> +++ b/hw/virtio/vhost-backend.c
> >>>> @@ -138,6 +138,12 @@ static int vhost_kernel_set_vring_call(struct
> >>>> vhost_dev *dev,
> >>>> return vhost_kernel_call(dev, VHOST_SET_VRING_CALL, file);
> >>>> }
> >>>> +static int vhost_kernel_set_vring_busyloop_timeout(struct vhost_dev
> >>>> *dev,
> >>>> + struct
> >>>> vhost_vring_state *s)
> >>>> +{
> >>>> + return vhost_kernel_call(dev, VHOST_SET_VRING_BUSYLOOP_TIMEOUT, s);
> >>>> +}
> >>>> +
> >>>> static int vhost_kernel_set_features(struct vhost_dev *dev,
> >>>> uint64_t features)
> >>>> {
> >>>> @@ -185,6 +191,8 @@ static const VhostOps kernel_ops = {
> >>>> .vhost_get_vring_base = vhost_kernel_get_vring_base,
> >>>> .vhost_set_vring_kick = vhost_kernel_set_vring_kick,
> >>>> .vhost_set_vring_call = vhost_kernel_set_vring_call,
> >>>> + .vhost_set_vring_busyloop_timeout =
> >>>> + vhost_kernel_set_vring_busyloop_timeout,
> >>>> .vhost_set_features = vhost_kernel_set_features,
> >>>> .vhost_get_features = vhost_kernel_get_features,
> >>>> .vhost_set_owner = vhost_kernel_set_owner,
> >>>> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> >>>> index 4400718..ebf8b08 100644
> >>>> --- a/hw/virtio/vhost.c
> >>>> +++ b/hw/virtio/vhost.c
> >>>> @@ -964,6 +964,28 @@ static void vhost_eventfd_del(MemoryListener
> >>>> *listener,
> >>>> {
> >>>> }
> >>>> +static int vhost_virtqueue_set_busyloop_timeout(struct vhost_dev *dev,
> >>>> + int n, uint32_t timeout)
> >>>> +{
> >>>> + int vhost_vq_index = dev->vhost_ops->vhost_get_vq_index(dev, n);
> >>>> + struct vhost_vring_state state = {
> >>>> + .index = vhost_vq_index,
> >>>> + .num = timeout,
> >>>> + };
> >>>> + int r;
> >>>> +
> >>>> + if (!dev->vhost_ops->vhost_set_vring_busyloop_timeout) {
> >>>> + return -EINVAL;
> >>>> + }
> >>>> +
> >>>> + r = dev->vhost_ops->vhost_set_vring_busyloop_timeout(dev, &state);
> >>>> + if (r) {
> >>>> + return r;
> >>>> + }
> >>>> +
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> static int vhost_virtqueue_init(struct vhost_dev *dev,
> >>>> struct vhost_virtqueue *vq, int n)
> >>>> {
> >>>> @@ -994,7 +1016,7 @@ static void vhost_virtqueue_cleanup(struct
> >>>> vhost_virtqueue *vq)
> >>>> }
> >>>> int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
> >>>> - VhostBackendType backend_type)
> >>>> + VhostBackendType backend_type, uint32_t
> >>>> busyloop_timeout)
> >>>> {
> >>>> uint64_t features;
> >>>> int i, r;
> >>>> @@ -1035,6 +1057,17 @@ int vhost_dev_init(struct vhost_dev *hdev, void
> >>>> *opaque,
> >>>> goto fail_vq;
> >>>> }
> >>>> }
> >>>> +
> >>>> + if (busyloop_timeout) {
> >>>> + for (i = 0; i < hdev->nvqs; ++i) {
> >>>> + r = vhost_virtqueue_set_busyloop_timeout(hdev,
> >>>> hdev->vq_index + i,
> >>>> + busyloop_timeout);
> >>>> + if (r < 0) {
> >>>> + goto fail_busyloop;
> >>>> + }
> >>>> + }
> >>>> + }
> >>>> +
> >>>> hdev->features = features;
> >>>> hdev->memory_listener = (MemoryListener) {
> >>>> @@ -1077,6 +1110,11 @@ int vhost_dev_init(struct vhost_dev *hdev, void
> >>>> *opaque,
> >>>> hdev->memory_changed = false;
> >>>> memory_listener_register(&hdev->memory_listener,
> >>>> &address_space_memory);
> >>>> return 0;
> >>>> +fail_busyloop:
> >>>> + while (--i >= 0) {
> >>>> + vhost_virtqueue_set_busyloop_timeout(hdev, hdev->vq_index + i,
> >>>> 0);
> >>>> + }
> >>>> + i = hdev->nvqs;
> >>>> fail_vq:
> >>>> while (--i >= 0) {
> >>>> vhost_virtqueue_cleanup(hdev->vqs + i);
> >>>> diff --git a/include/hw/virtio/vhost-backend.h
> >>>> b/include/hw/virtio/vhost-backend.h
> >>>> index 95fcc96..84e1cb7 100644
> >>>> --- a/include/hw/virtio/vhost-backend.h
> >>>> +++ b/include/hw/virtio/vhost-backend.h
> >>>> @@ -57,6 +57,8 @@ typedef int (*vhost_set_vring_kick_op)(struct
> >>>> vhost_dev *dev,
> >>>> struct vhost_vring_file *file);
> >>>> typedef int (*vhost_set_vring_call_op)(struct vhost_dev *dev,
> >>>> struct vhost_vring_file *file);
> >>>> +typedef int (*vhost_set_vring_busyloop_timeout_op)(struct vhost_dev
> >>>> *dev,
> >>>> + struct
> >>>> vhost_vring_state *r);
> >>>> typedef int (*vhost_set_features_op)(struct vhost_dev *dev,
> >>>> uint64_t features);
> >>>> typedef int (*vhost_get_features_op)(struct vhost_dev *dev,
> >>>> @@ -91,6 +93,7 @@ typedef struct VhostOps {
> >>>> vhost_get_vring_base_op vhost_get_vring_base;
> >>>> vhost_set_vring_kick_op vhost_set_vring_kick;
> >>>> vhost_set_vring_call_op vhost_set_vring_call;
> >>>> + vhost_set_vring_busyloop_timeout_op
> >>>> vhost_set_vring_busyloop_timeout;
> >>>> vhost_set_features_op vhost_set_features;
> >>>> vhost_get_features_op vhost_get_features;
> >>>> vhost_set_owner_op vhost_set_owner;
> >>>> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> >>>> index b60d758..2106ed8 100644
> >>>> --- a/include/hw/virtio/vhost.h
> >>>> +++ b/include/hw/virtio/vhost.h
> >>>> @@ -64,7 +64,8 @@ struct vhost_dev {
> >>>> };
> >>>> int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
> >>>> - VhostBackendType backend_type);
> >>>> + VhostBackendType backend_type,
> >>>> + uint32_t busyloop_timeout);
> >>>> void vhost_dev_cleanup(struct vhost_dev *hdev);
> >>>> int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev);
> >>>> void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev);
> >>>> diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
> >>>> index 3389b41..8354b98 100644
> >>>> --- a/include/net/vhost_net.h
> >>>> +++ b/include/net/vhost_net.h
> >>>> @@ -10,6 +10,7 @@ typedef struct vhost_net VHostNetState;
> >>>> typedef struct VhostNetOptions {
> >>>> VhostBackendType backend_type;
> >>>> NetClientState *net_backend;
> >>>> + uint32_t busyloop_timeout;
> >>>> void *opaque;
> >>>> } VhostNetOptions;
> >>>> diff --git a/net/tap.c b/net/tap.c
> >>>> index 740e8a2..7e28102 100644
> >>>> --- a/net/tap.c
> >>>> +++ b/net/tap.c
> >>>> @@ -663,6 +663,11 @@ static void net_init_tap_one(const NetdevTapOptions
> >>>> *tap, NetClientState *peer,
> >>>> options.backend_type = VHOST_BACKEND_TYPE_KERNEL;
> >>>> options.net_backend = &s->nc;
> >>>> + if (tap->has_vhost_poll_us) {
> >>>> + options.busyloop_timeout = tap->vhost_poll_us;
> >>>> + } else {
> >>>> + options.busyloop_timeout = 0;
> >>>> + }
> >>>> if (vhostfdname) {
> >>>> vhostfd = monitor_fd_param(cur_mon, vhostfdname, &err);
> >>>> @@ -686,8 +691,9 @@ static void net_init_tap_one(const NetdevTapOptions
> >>>> *tap, NetClientState *peer,
> >>>> "vhost-net requested but could not be
> >>>> initialized");
> >>>> return;
> >>>> }
> >>>> - } else if (vhostfdname) {
> >>>> - error_setg(errp, "vhostfd= is not valid without vhost");
> >>>> + } else if (vhostfdname || tap->has_vhost_poll_us) {
> >>>> + error_setg(errp, "vhostfd(s)= or vhost_poll_us= is not valid"
> >>>> + " without vhost");
> >>>> }
> >>>> }
> >>>> diff --git a/net/vhost-user.c b/net/vhost-user.c
> >>>> index 1b9e73a..b200182 100644
> >>>> --- a/net/vhost-user.c
> >>>> +++ b/net/vhost-user.c
> >>>> @@ -80,6 +80,7 @@ static int vhost_user_start(int queues, NetClientState
> >>>> *ncs[])
> >>>> options.net_backend = ncs[i];
> >>>> options.opaque = s->chr;
> >>>> + options.busyloop_timeout = 0;
> >>>> s->vhost_net = vhost_net_init(&options);
> >>>> if (!s->vhost_net) {
> >>>> error_report("failed to init vhost_net for queue %d", i);
> >>>> diff --git a/qapi-schema.json b/qapi-schema.json
> >>>> index 54634c4..8afdedf 100644
> >>>> --- a/qapi-schema.json
> >>>> +++ b/qapi-schema.json
> >>>> @@ -2531,6 +2531,9 @@
> >>>> #
> >>>> # @queues: #optional number of queues to be created for multiqueue
> >>>> capable tap
> >>>> #
> >>>> +# @vhost-poll-us: #optional maximum number of microseconds that could
> >>>> +# be spent on busy polling for vhost net (since 2.7)
> >>>> +#
> >>>> # Since 1.2
> >>>> ##
> >>>> { 'struct': 'NetdevTapOptions',
> >>>> @@ -2547,7 +2550,8 @@
> >>>> '*vhostfd': 'str',
> >>>> '*vhostfds': 'str',
> >>>> '*vhostforce': 'bool',
> >>>> - '*queues': 'uint32'} }
> >>>> + '*queues': 'uint32',
> >>>> + '*vhost-poll-us': 'uint32'} }
> >>>> ##
> >>>> # @NetdevSocketOptions
> >>>> diff --git a/qemu-options.hx b/qemu-options.hx
> >>>> index 587de8f..22ddb82 100644
> >>>> --- a/qemu-options.hx
> >>>> +++ b/qemu-options.hx
> >>>> @@ -1569,6 +1569,7 @@ DEF("netdev", HAS_ARG, QEMU_OPTION_netdev,
> >>>> "-netdev
> >>>> tap,id=str[,fd=h][,fds=x:y:...:z][,ifname=name][,script=file][,downscript=dfile]\n"
> >>>> "
> >>>> [,helper=helper][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off]\n"
> >>>> "
> >>>> [,vhostfd=h][,vhostfds=x:y:...:z][,vhostforce=on|off][,queues=n]\n"
> >>>> + " [,vhost-poll-us=n]\n"
> >>>> " configure a host TAP network backend with ID
> >>>> 'str'\n"
> >>>> " use network scripts 'file' (default="
> >>>> DEFAULT_NETWORK_SCRIPT ")\n"
> >>>> " to configure it and 'dfile' (default="
> >>>> DEFAULT_NETWORK_DOWN_SCRIPT ")\n"
> >>>> @@ -1588,6 +1589,8 @@ DEF("netdev", HAS_ARG, QEMU_OPTION_netdev,
> >>>> " use 'vhostfd=h' to connect to an already opened
> >>>> vhost net device\n"
> >>>> " use 'vhostfds=x:y:...:z to connect to multiple
> >>>> already opened vhost net devices\n"
> >>>> " use 'queues=n' to specify the number of queues to
> >>>> be created for multiqueue TAP\n"
> >>>> + " use 'vhost-poll-us=n' to speciy the maximum number
> >>>> of microseconds that could be\n"
> > typo above
> >
> >>>> + " spent on busy polling for vhost net\n"
> >>>> "-netdev bridge,id=str[,br=bridge][,helper=helper]\n"
> >>>> " configure a host TAP network backend with ID
> >>>> 'str' that is\n"
> >>>> " connected to a bridge (default="
> >>>> DEFAULT_BRIDGE_INTERFACE ")\n"
> >>>> --
> >>>> 2.5.0
>
>
