On Mon, Jul 16, 2018 at 05:46:33PM +0800, Jason Wang wrote: > > > On 2018年07月16日 16:39, Michael S. Tsirkin wrote: > > On Mon, Jul 16, 2018 at 11:28:03AM +0800, Jason Wang wrote: > > > Hi all: > > > > > > This series implements packed virtqueues. The code were tested with > > > Tiwei's guest driver series at https://patchwork.ozlabs.org/cover/942297/ > > > > > > > > > Pktgen test for both RX and TX does not show obvious difference with > > > split virtqueues. The main bottleneck is the guest Linux driver, since > > > it can not stress vhost for a 100% CPU utilization. A full TCP > > > benchmark is ongoing. Will test virtio-net pmd as well when it was > > > ready. > > Well the question then is why we should bother merging this > > if this doesn't give a performance gain. > > We meet bottlenecks at other places. I can only test Linux driver which has > lots of overheads e.g interrupts. And perf show only a small fraction of > time were spent on e.g virtqueue manipulation. I hope virtio-net pmd can > give us different result but we don't have one ready for testing now. (Jen's > V4 have bugs thus can not work with this series). Can't linux busy poll? And how about testing loopback with XDP? > > Do you see > > a gain in CPU utilization maybe? > > Unfortunately not. > > > > > If not - let's wait for that TCP benchmark result? > > We can, but you know TCP_STREAM result is sometime misleading. > > A brunch of other patches of mine were rebased on this and then blocked on > this series. Consider we don't meet regression, maybe we can merge this > first and try optimizations or fixups on top? > > Thanks I'm not sure I understand this approach. Packed ring is just an optimization. What value is there in merging it if it does not help speed? > > > > > Notes: > > > - This version depends on Tiwei's series at https://patchwork.ozlabs.org/cover/942297/ > > > > > > This version were tested with: > > > > > > - Zerocopy (Out of Order) support > > > - vIOMMU support > > > - mergeable buffer on/off > > > - busy polling on/off > > > - vsock (nc-vsock) > > > > > > Changes from V1: > > > - drop uapi patch and use Tiwei's > > > - split the enablement of packed virtqueue into a separate patch > > > > > > Changes from RFC V5: > > > > > > - save unnecessary barriers during vhost_add_used_packed_n() > > > - more compact math for event idx > > > - fix failure of SET_VRING_BASE when avail_wrap_counter is true > > > - fix not copy avail_wrap_counter during GET_VRING_BASE > > > - introduce SET_VRING_USED_BASE/GET_VRING_USED_BASE for syncing last_used_idx > > > - rename used_wrap_counter to last_used_wrap_counter > > > - rebase to net-next > > > > > > Changes from RFC V4: > > > > > > - fix signalled_used index recording > > > - track avail index correctly > > > - various minor fixes > > > > > > Changes from RFC 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 RFC 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 RFC 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 > > > vhost: packed ring support > > > vhost: event suppression for packed ring > > > vhost: enable packed virtqueues > > > > > > drivers/vhost/net.c | 143 ++----- > > > drivers/vhost/scsi.c | 62 +-- > > > drivers/vhost/vhost.c | 994 ++++++++++++++++++++++++++++++++++++++++----- > > > drivers/vhost/vhost.h | 55 ++- > > > drivers/vhost/vsock.c | 42 +- > > > include/uapi/linux/vhost.h | 7 + > > > 6 files changed, 1035 insertions(+), 268 deletions(-) > > > > > > -- > > > 2.7.4
