Re: [RFC V4 PATCH 0/8] Packed ring layout for vhost

[Jason Wang]

On 2018å05æ21æ 00:25, Wei Xu wrote:
> On Wed, May 16, 2018 at 08:32:13PM +0800, Jason Wang wrote:
> > Hi all:
> >
> > This RFC implement packed ring layout. The code were tested with
> > Tiwei's RFC V3 ahttps://lkml.org/lkml/2018/4/25/34. Some fixups and
> > tweaks were needed on top of Tiwei's code to make it run for event
> > index.
> Could you please show the change based on Tiwei's code to easy other's
> test?

Please try Tiwei's V4 instead of just waiting for the fixup. It should 
work unless you don't try zerocopy and vIOMMU.


> > Pktgen reports about 20% improvement on PPS (event index is off). More
> > testing is ongoing.
> >
> > Notes for tester:
> >
> > - Start from this version, vhost need qemu co-operation to work
> >    correctly. Or you can comment out the packed specific code for
> >    GET/SET_VRING_BASE.
> Do you mean the code in vhost_virtqueue_start/stop?

For qemu, probably.

> Both Tiwei's and your v3
> work fortunately correctly which should be avoided since the ring should be
> definitely different.

I don't understand this, you mean reset work?

Thanks

> Wei
>
> > Changes from V3:
> > - Fix math on event idx checking
> > - Sync last avail wrap counter through GET/SET_VRING_BASE
> > - remove desc_event prefix in the driver/device structure
> >
> > Changes from V2:
> > - do not use & in checking desc_event_flags
> > - off should be most significant bit
> > - remove the workaround of mergeable buffer for dpdk prototype
> > - id should be in the last descriptor in the chain
> > - keep _F_WRITE for write descriptor when adding used
> > - device flags updating should use ADDR_USED type
> > - return error on unexpected unavail descriptor in a chain
> > - return false in vhost_ve_avail_empty is descriptor is available
> > - track last seen avail_wrap_counter
> > - correctly examine available descriptor in get_indirect_packed()
> > - vhost_idx_diff should return u16 instead of bool
> >
> > Changes from V1:
> >
> > - Refactor vhost used elem code to avoid open coding on used elem
> > - Event suppression support (compile test only).
> > - Indirect descriptor support (compile test only).
> > - Zerocopy support.
> > - vIOMMU support.
> > - SCSI/VSOCK support (compile test only).
> > - Fix several bugs
> >
> > Jason Wang (8):
> >    vhost: move get_rx_bufs to vhost.c
> >    vhost: hide used ring layout from device
> >    vhost: do not use vring_used_elem
> >    vhost_net: do not explicitly manipulate vhost_used_elem
> >    vhost: vhost_put_user() can accept metadata type
> >    virtio: introduce packed ring defines
> >    vhost: packed ring support
> >    vhost: event suppression for packed ring
> >
> >   drivers/vhost/net.c                | 136 ++----
> >   drivers/vhost/scsi.c               |  62 +--
> >   drivers/vhost/vhost.c              | 861 ++++++++++++++++++++++++++++++++-----
> >   drivers/vhost/vhost.h              |  47 +-
> >   drivers/vhost/vsock.c              |  42 +-
> >   include/uapi/linux/virtio_config.h |   9 +
> >   include/uapi/linux/virtio_ring.h   |  32 ++
> >   7 files changed, 928 insertions(+), 261 deletions(-)
> >
> > --
> > 2.7.4