[ovs-dev] [PATCH v2 1/4] netdev-dpdk: fix mempool management with vhu client.

Fischetti, Antonio antonio.fischetti at intel.com
Tue Oct 3 15:25:26 UTC 2017


Thanks Kevin for your feedback.
Below some details on what happens, how to replicate the issue and 
some comments inline.

-Antonio

> -----Original Message-----
> From: Kevin Traynor [mailto:ktraynor at redhat.com]
> Sent: Monday, October 2, 2017 6:38 PM
> To: Fischetti, Antonio <antonio.fischetti at intel.com>; dev at openvswitch.org
> Cc: Aaron Conole <aconole at redhat.com>
> Subject: Re: [PATCH v2 1/4] netdev-dpdk: fix mempool management with vhu
> client.
> 
> On 09/28/2017 03:28 PM, antonio.fischetti at intel.com wrote:
> > From: Antonio Fischetti <antonio.fischetti at intel.com>
> >
> > In a PVP test where vhostuser ports are configured as
> > clients, OvS crashes when QEMU is launched.
> > This patch avoids the repeated calls to netdev_change_seq_changed
> > after the requested mempool is already acquired.
> >
> 
> Can you explain what is happening in this bug? I can't reproduce it 

[Antonio]
When QEMU is being launched, ovs crashes with the following stacktrace:
https://mail.openvswitch.org/pipermail/ovs-dev/2017-September/339343.html

In case the requested mempool already exists, netdev_dpdk_mempool_configure
returns 0 => netdev_change_seq_changed is called.

The issue happens with vhostuser 'client' ports:
 - the vhu ports must be of dpdkvhostuserclient type
 - so the QEMU command must contain 'server' like
   qemu-system-x86_64 .... path=$CLIENT_SOCK_DIR/$SOCK0,server

Below other details on my setup.

  1 PMD
  -----
ovs-vsctl --no-wait set Open_vSwitch . other_config:pmd-cpu-mask=8

  Ports
  -----
ovs-vsctl add-port br0 dpdk0 -- set Interface dpdk0 type=dpdk options:dpdk-devargs=$NIC0
ovs-vsctl add-port br0 dpdk0 -- set Interface dpdk1 type=dpdk options:dpdk-devargs=$NIC1

ovs-vsctl add-port br0 dpdkvhostuser0 -- set Interface dpdkvhostuser0 type=dpdkvhostuserclient
ovs-vsctl set Interface dpdkvhostuser0 options:vhost-server-path="/tmp/dpdkvhostuser0"

ovs-vsctl add-port br0 dpdkvhostuser1 -- set Interface dpdkvhostuser1 type=dpdkvhostuserclient
ovs-vsctl set Interface dpdkvhostuser1 options:vhost-server-path="/tmp/dpdkvhostuser1"


I'm using DPDK v17.05 and QEMU v2.7.0.


Other details are below right after the patch description.



> and
> the mempool for vhost ports should only be reconfigured if the number of
> queues or socket has changed.
> 
> > CC: Kevin Traynor <ktraynor at redhat.com>
> > CC: Aaron Conole <aconole at redhat.com>
> > Reported-by: Ciara Loftus <ciara.loftus at intel.com>
> > Fixes: d555d9bded5f ("netdev-dpdk: Create separate memory pool for each
> port.")
> > Signed-off-by: Antonio Fischetti <antonio.fischetti at intel.com>
> > ---
> > To replicate the bug scenario:
> >
> >  PVP test setup
> >  --------------
> > CLIENT_SOCK_DIR=/tmp
> > SOCK0=dpdkvhostuser0
> > SOCK1=dpdkvhostuser1
> >
> > 1 PMD
> > Add 2 dpdk ports, n_rxq=1
> > Add 2 vhu ports both of type dpdkvhostuserclient and specify vhost-server-
> path
> >  ovs-vsctl set Interface dpdkvhostuser0 options:vhost-server-
> path="$CLIENT_SOCK_DIR/$SOCK0"
> >  ovs-vsctl set Interface dpdkvhostuser1 options:vhost-server-
> path="$CLIENT_SOCK_DIR/$SOCK1"
> >
> > Set port-based rules: dpdk0 <--> vhu0 and dpdk1 <--> vhu1
> >  add-flow br0 in_port=1,action=output:3
> >  add-flow br0 in_port=3,action=output:1
> >  add-flow br0 in_port=4,action=output:2
> >  add-flow br0 in_port=2,action=output:4
> >
> >  Launch QEMU
> >  -----------
> > As OvS vhu ports are acting as clients, we must specify 'server' in the next
> command.
> > VM_IMAGE=<path/to/your/vm/image>
> >
> >  sudo -E taskset 0x3F00 $QEMU_DIR/x86_64-softmmu/qemu-system-x86_64 -name us-
> vhost-vm1 -cpu host -enable-kvm -m 4096M -object memory-backend-
> file,id=mem,size=4096M,mem-path=/dev/hugepages,share=on -numa node,memdev=mem -
> mem-prealloc -smp 4 -drive file=$VM_IMAGE -chardev
> socket,id=char0,path=$CLIENT_SOCK_DIR/$SOCK0,server -netdev type=vhost-
> user,id=mynet1,chardev=char0,vhostforce -device virtio-net-
> pci,mac=00:00:00:00:00:01,netdev=mynet1,mrg_rxbuf=off -chardev
> socket,id=char1,path=$CLIENT_SOCK_DIR/$SOCK1,server -netdev type=vhost-
> user,id=mynet2,chardev=char1,vhostforce -device virtio-net-
> pci,mac=00:00:00:00:00:02,netdev=mynet2,mrg_rxbuf=off --nographic
> >
> >  Expected behavior
> >  -----------------
> > With this fix OvS shouldn't crash.
> > ---
> >  lib/netdev-dpdk.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
> > index c60f46f..dda3771 100644
> > --- a/lib/netdev-dpdk.c
> > +++ b/lib/netdev-dpdk.c
> > @@ -621,6 +621,10 @@ netdev_dpdk_mempool_configure(struct netdev_dpdk *dev)
> >      uint32_t buf_size = dpdk_buf_size(dev->requested_mtu);
> >      struct dpdk_mp *mp;
> >
> > +    if (dev->requested_socket_id == dev->socket_id
> > +        && dev->requested_mtu == dev->mtu) {
> > +        return EEXIST;
> > +    }
> 
> But you would want to get a new mempool if the number of queues have
> changed, as that is part of the calculation for the size of the mempool.
> MIN_NB_MBUF was added to over provision as a safety so you'd probably
> get away with it but you should be requesting a new mempool with the
> correctly calculated num of mbufs.

[Antonio] I get your point, if the nr of queues has changed, then
socket and mtu are unchanged. But a new nr of mbuf must be computed
to accommodate packets for the different queues. That affects the
mp name too. So we do need to call dpdk_mp_create to create a new
mp.


> 
> It seems like this code is trying to add back in the code to prevent
> rte_pktmbuf_pool_create being called again for the same values. In the
> patchset that this fixes it is removed and the EEXISTS return from
> rte_pktmbuf_pool_create are handled instead. I'm not sure that both
> mechanisms are needed.

[Antonio] I'll try to rework by managing the EEXIST case only.

> 
> >      mp = dpdk_mp_get(dev, FRAME_LEN_TO_MTU(buf_size));
> >      if (!mp) {
> >          VLOG_ERR("Failed to create memory pool for netdev "
> > @@ -3207,7 +3211,7 @@ netdev_dpdk_reconfigure(struct netdev *netdev)
> >      rte_eth_dev_stop(dev->port_id);
> >
> >      err = netdev_dpdk_mempool_configure(dev);
> > -    if (err) {
> > +    if (err && err != EEXIST) {
> >          goto out;
> >      }
> >
> > @@ -3247,10 +3251,10 @@ dpdk_vhost_reconfigure_helper(struct netdev_dpdk
> *dev)
> >      netdev_dpdk_remap_txqs(dev);
> >
> >      err = netdev_dpdk_mempool_configure(dev);
> > -    if (err) {
> > -        return err;
> > -    } else {
> > +    if (!err) {
> >          netdev_change_seq_changed(&dev->up);
> > +    } else if (err != EEXIST){
> > +        return err;
> >      }
> >
> >      if (netdev_dpdk_get_vid(dev) >= 0) {
> >



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