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...rformance on x86 in the > Haswell+ era: > https://groups.google.com/forum/#!topic/snabb-devel/aez4pEnd4ow Thanks. I've been thinking about how to eliminate the VM <-> host <-> VM switching and instead achieve just VM <-> VM. The holy grail of VM-to-VM networking is an exitless I/O path. In other words, packets can be transferred between VMs without any vmexits (this requires a polling driver). Here is how it works. QEMU gets "-device vhost-user" so that a VM can act as the vhost-user server: VM1 (virtio-net guest driver) <-> VM2 (vhost-user device) V...

...rformance on x86 in the > Haswell+ era: > https://groups.google.com/forum/#!topic/snabb-devel/aez4pEnd4ow Thanks. I've been thinking about how to eliminate the VM <-> host <-> VM switching and instead achieve just VM <-> VM. The holy grail of VM-to-VM networking is an exitless I/O path. In other words, packets can be transferred between VMs without any vmexits (this requires a polling driver). Here is how it works. QEMU gets "-device vhost-user" so that a VM can act as the vhost-user server: VM1 (virtio-net guest driver) <-> VM2 (vhost-user device) V...

...ra: >> https://groups.google.com/forum/#!topic/snabb-devel/aez4pEnd4ow > > Thanks. > > I've been thinking about how to eliminate the VM <-> host <-> VM > switching and instead achieve just VM <-> VM. > > The holy grail of VM-to-VM networking is an exitless I/O path. In > other words, packets can be transferred between VMs without any > vmexits (this requires a polling driver). > > Here is how it works. QEMU gets "-device vhost-user" so that a VM can > act as the vhost-user server: > > VM1 (virtio-net guest driver) &...

...snabb-devel/aez4pEnd4ow >>> >>> Thanks. >>> >>> I've been thinking about how to eliminate the VM <-> host <-> VM >>> switching and instead achieve just VM <-> VM. >>> >>> The holy grail of VM-to-VM networking is an exitless I/O path. In >>> other words, packets can be transferred between VMs without any >>> vmexits (this requires a polling driver). >>> >>> Here is how it works. QEMU gets "-device vhost-user" so that a VM can >>> act as the vhost-user server: &gt...

...snabb-devel/aez4pEnd4ow >>> >>> Thanks. >>> >>> I've been thinking about how to eliminate the VM <-> host <-> VM >>> switching and instead achieve just VM <-> VM. >>> >>> The holy grail of VM-to-VM networking is an exitless I/O path. In >>> other words, packets can be transferred between VMs without any >>> vmexits (this requires a polling driver). >>> >>> Here is how it works. QEMU gets "-device vhost-user" so that a VM can >>> act as the vhost-user server: &gt...

...ps.google.com/forum/#!topic/snabb-devel/aez4pEnd4ow >> >> Thanks. >> >> I've been thinking about how to eliminate the VM <-> host <-> VM >> switching and instead achieve just VM <-> VM. >> >> The holy grail of VM-to-VM networking is an exitless I/O path. In >> other words, packets can be transferred between VMs without any >> vmexits (this requires a polling driver). >> >> Here is how it works. QEMU gets "-device vhost-user" so that a VM can >> act as the vhost-user server: >> >> VM1 (...

...ps.google.com/forum/#!topic/snabb-devel/aez4pEnd4ow >> >> Thanks. >> >> I've been thinking about how to eliminate the VM <-> host <-> VM >> switching and instead achieve just VM <-> VM. >> >> The holy grail of VM-to-VM networking is an exitless I/O path. In >> other words, packets can be transferred between VMs without any >> vmexits (this requires a polling driver). >> >> Here is how it works. QEMU gets "-device vhost-user" so that a VM can >> act as the vhost-user server: >> >> VM1 (...

...>>> >>>> Thanks. >>>> >>>> I've been thinking about how to eliminate the VM <-> host <-> VM >>>> switching and instead achieve just VM <-> VM. >>>> >>>> The holy grail of VM-to-VM networking is an exitless I/O path. In >>>> other words, packets can be transferred between VMs without any >>>> vmexits (this requires a polling driver). >>>> >>>> Here is how it works. QEMU gets "-device vhost-user" so that a VM can >>>> act as the vh...

...e we are better off returning to the exit-based notification > mechanism. The default timeout of 3 seconds can be changed with the > "poll_stop_idle" kernel module parameter. > > This polling approach makes lot of sense for new HW with posted-interrupts for > which we have exitless host-to-guest notifications. But even with support for > posted interrupts, guest-to-host communication still causes exits. Polling adds > the missing part. > > When systems are overloaded, there won't be enough cpu time for the various > vhost threads to poll their guests'...

On Fri, Apr 24, 2015 at 1:17 PM, Luke Gorrie <luke at snabb.co> wrote: > On 24 April 2015 at 11:47, Stefan Hajnoczi <stefanha at gmail.com> wrote: >> >> My concern is the overhead of the vhost_net component copying >> descriptors between NICs. > > > I see. So you would not have to reserve CPU resources for vswitches. Instead > you would give all cores

On Fri, Apr 24, 2015 at 1:17 PM, Luke Gorrie <luke at snabb.co> wrote: > On 24 April 2015 at 11:47, Stefan Hajnoczi <stefanha at gmail.com> wrote: >> >> My concern is the overhead of the vhost_net component copying >> descriptors between NICs. > > > I see. So you would not have to reserve CPU resources for vswitches. Instead > you would give all cores

...new work, as in this case we are better off returning to the exit-based notification mechanism. The default timeout of 3 seconds can be changed with the "poll_stop_idle" kernel module parameter. This polling approach makes lot of sense for new HW with posted-interrupts for which we have exitless host-to-guest notifications. But even with support for posted interrupts, guest-to-host communication still causes exits. Polling adds the missing part. When systems are overloaded, there won't be enough cpu time for the various vhost threads to poll their guests' devices. For these scenar...

...new work, as in this case we are better off returning to the exit-based notification mechanism. The default timeout of 3 seconds can be changed with the "poll_stop_idle" kernel module parameter. This polling approach makes lot of sense for new HW with posted-interrupts for which we have exitless host-to-guest notifications. But even with support for posted interrupts, guest-to-host communication still causes exits. Polling adds the missing part. When systems are overloaded, there won't be enough cpu time for the various vhost threads to poll their guests' devices. For these scenar...

...ING_F_EVENT_ENABLE 0x0 > > #define VRING_F_EVENT_DISABLE 0x1 > > Event index includes the index of the descriptor > which should trigger the event, and the wrap counter > in the high bit. Not specific to v3, but looks like with event index, we can't achieve interruptless or exitless consider idx may wrap. > > In that case, interrupt triggers when descriptor is written at a given > location in the ring (or skipped in case of NEXT/MORE). > > If both features are negotiated, a special flags value > can be used to switch to event idx: > > #define VRING_F_E...

...e we are better off returning to the exit-based notification > mechanism. The default timeout of 3 seconds can be changed with the > "poll_stop_idle" kernel module parameter. > > This polling approach makes lot of sense for new HW with posted-interrupts for > which we have exitless host-to-guest notifications. But even with support for > posted interrupts, guest-to-host communication still causes exits. Polling adds > the missing part. > > When systems are overloaded, there won't be enough cpu time for the various > vhost threads to poll their guests'...

...e we are better off returning to the exit-based notification > mechanism. The default timeout of 3 seconds can be changed with the > "poll_stop_idle" kernel module parameter. > > This polling approach makes lot of sense for new HW with posted-interrupts for > which we have exitless host-to-guest notifications. But even with support for > posted interrupts, guest-to-host communication still causes exits. Polling adds > the missing part. > > When systems are overloaded, there won't be enough cpu time for the various > vhost threads to poll their guests'...

This is an update from v1 version. Changes: - update event suppression mechanism - separate options for indirect and direct s/g - lots of new features --- Performance analysis of this is in my kvm forum 2016 presentation. The idea is to have a r/w descriptor in a ring structure, replacing the used and available ring, index and descriptor buffer. * Descriptor ring: Guest adds descriptors with

This is an update from v1 version. Changes: - update event suppression mechanism - separate options for indirect and direct s/g - lots of new features --- Performance analysis of this is in my kvm forum 2016 presentation. The idea is to have a r/w descriptor in a ring structure, replacing the used and available ring, index and descriptor buffer. * Descriptor ring: Guest adds descriptors with