On Thu, Aug 13, 2015 at 12:18:38PM +0300, Michael S. Tsirkin wrote:
> On Wed, Aug 12, 2015 at 02:25:41PM +0800, Ouyang Changchun wrote:
> > Based on patch by Nikolay Nikolaev:
> > Vhost-user will implement the multi queue support in a similar way
> > to what vhost already has - a separate thread for each queue.
> > To enable the multi queue functionality - a new command line parameter
> > "queues" is introduced for the vhost-user netdev.
> >
> > The RESET_OWNER change is based on commit:
> > 294ce717e0f212ed0763307f3eab72b4a1bdf4d0
> > If it is reverted, the patch need update for it accordingly.
> >
> > Signed-off-by: Nikolay Nikolaev <n.nikol...@virtualopensystems.com>
> > Signed-off-by: Changchun Ouyang <changchun.ouy...@intel.com>
[snip...]
> > @@ -198,7 +203,7 @@ Message types
> >
> > Id: 4
> > Equivalent ioctl: VHOST_RESET_OWNER
> > - Master payload: N/A
> > + Master payload: vring state description
> >
> > Issued when a new connection is about to be closed. The Master will
> > no
> > longer own this connection (and will usually close it).
>
> This is an interface change, isn't it?
> We can't make it unconditionally, need to make it dependent
> on a protocol flag.
Hi Michael,
I'm wondering why we need a payload here, as we don't do that for
VHOST_SET_OWNER. I mean, stopping one or few queue pairs when a
connect is about to be close doesn't make sense to me. Instead,
we should clean up all queue pair when VHOST_RESET_OWNER message
is received, right?
>
>
> > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> > index 1f25cb3..9cd6c05 100644
> > --- a/hw/net/vhost_net.c
> > +++ b/hw/net/vhost_net.c
[snip...]
> > static int net_vhost_user_init(NetClientState *peer, const char *device,
> > - const char *name, CharDriverState *chr)
> > + const char *name, CharDriverState *chr,
> > + uint32_t queues)
> > {
> > NetClientState *nc;
> > VhostUserState *s;
> > + int i;
> >
> > - nc = qemu_new_net_client(&net_vhost_user_info, peer, device, name);
> > + for (i = 0; i < queues; i++) {
> > + nc = qemu_new_net_client(&net_vhost_user_info, peer, device, name);
> >
> > - snprintf(nc->info_str, sizeof(nc->info_str), "vhost-user to %s",
> > - chr->label);
> > + snprintf(nc->info_str, sizeof(nc->info_str), "vhost-user%d to %s",
> > + i, chr->label);
> >
> > - s = DO_UPCAST(VhostUserState, nc, nc);
> > + s = DO_UPCAST(VhostUserState, nc, nc);
> >
> > - /* We don't provide a receive callback */
> > - s->nc.receive_disabled = 1;
> > - s->chr = chr;
> > -
> > - qemu_chr_add_handlers(s->chr, NULL, NULL, net_vhost_user_event, s);
> > + /* We don't provide a receive callback */
> > + s->nc.receive_disabled = 1;
> > + s->chr = chr;
> > + s->nc.queue_index = i;
> >
> > + qemu_chr_add_handlers(s->chr, NULL, NULL, net_vhost_user_event, s);
> > + }
> > return 0;
> > }
> >
> > @@ -225,6 +229,7 @@ static int net_vhost_check_net(QemuOpts *opts, void
> > *opaque)
>
>
> There are two problems here:
>
> 1. we don't really know that the backend
> is able to support the requested number of queues.
> If not, everything will fail, silently.
> A new message to query the # of queues could help, though
> I'm not sure what can be done on failure. Fail connection?
What I'm thinking is we may do:
- introduce a feature flag, for indicating we support MQ or not.
We query this flag only when # of queues given is > 1. We exit
if it not matches.
- invoke vhost_dev init repeatedly for # of queues given, unless
something wrong happened, which basically means the backend
can not support such # of queues; we then quit.
We could, as you suggested, add an another message to query
the max # queues the backend support. However, judging we have
to check the return value of setting up a single queue pair,
which already gives feedback when the backed is not able to
support requested # of queues, we could save such message,
though it's easy to implement :)
>
> 2. each message (e.g. set memory table) is sent multiple times,
> on the same socket.
Yeah, for there is a single socket opening there, it's not necessary
to send messages like SET_MEM_TABLE multiple times. But for other
messages that relate to to a specific vring, we have to send N times,
don't we?
So, I'm wondering could we categorize the message in two types: vring
specific and none-vring specific. For vring specific, we send it N
times, with the vhost_dev->vq_index telling which one queue pair
we have interest.
For none-vring specific, we just send it once for first queue pair
(vhost_dev->queue == 0), just like what we did for tap: we launch
qemu-ifup/down script only for the first queue pair.
Comments? (And sorry if I made some silly comments, as I'm pretty
new to this community, say just have read about 2 weeks code).
--yliu
>
>
>
> > int net_init_vhost_user(const NetClientOptions *opts, const char *name,
> > NetClientState *peer)
> > {
> > + uint32_t queues;
> > const NetdevVhostUserOptions *vhost_user_opts;
> > CharDriverState *chr;
> >
> > @@ -243,6 +248,12 @@ int net_init_vhost_user(const NetClientOptions *opts,
> > const char *name,
> > return -1;
> > }
> >
> > + /* number of queues for multiqueue */
> > + if (vhost_user_opts->has_queues) {
> > + queues = vhost_user_opts->queues;
> > + } else {
> > + queues = 1;
> > + }
> >
> > - return net_vhost_user_init(peer, "vhost_user", name, chr);
> > + return net_vhost_user_init(peer, "vhost_user", name, chr, queues);
> > }
> > diff --git a/qapi-schema.json b/qapi-schema.json
> > index f97ffa1..51e40ce 100644
> > --- a/qapi-schema.json
> > +++ b/qapi-schema.json
> > @@ -2444,12 +2444,16 @@
> > #
> > # @vhostforce: #optional vhost on for non-MSIX virtio guests (default:
> > false).
> > #
> > +# @queues: #optional number of queues to be created for multiqueue
> > vhost-user
> > +# (default: 1) (Since 2.5)
> > +#
> > # Since 2.1
> > ##
> > { 'struct': 'NetdevVhostUserOptions',
> > 'data': {
> > 'chardev': 'str',
> > - '*vhostforce': 'bool' } }
> > + '*vhostforce': 'bool',
> > + '*queues': 'uint32' } }
> >
> > ##
> > # @NetClientOptions
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index ec356f6..dad035e 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -1942,13 +1942,14 @@ The hubport netdev lets you connect a NIC to a QEMU
> > "vlan" instead of a single
> > netdev. @code{-net} and @code{-device} with parameter @option{vlan}
> > create the
> > required hub automatically.
> >
> > -@item -netdev vhost-user,chardev=@var{id}[,vhostforce=on|off]
> > +@item -netdev vhost-user,chardev=@var{id}[,vhostforce=on|off][,queues=n]
> >
> > Establish a vhost-user netdev, backed by a chardev @var{id}. The chardev
> > should
> > be a unix domain socket backed one. The vhost-user uses a specifically
> > defined
> > protocol to pass vhost ioctl replacement messages to an application on the
> > other
> > end of the socket. On non-MSIX guests, the feature can be forced with
> > -@var{vhostforce}.
> > +@var{vhostforce}. Use 'queues=@var{n}' to specify the number of queues to
> > +be created for multiqueue vhost-user.
> >
> > Example:
> > @example
> > --
> > 1.8.4.2
> >
