[ovs-dev] [PATCHv2] netdev-afxdp: Add interrupt mode netdev class.

Ilya Maximets i.maximets at ovn.org
Fri Mar 6 16:11:24 UTC 2020


On 3/4/20 7:09 PM, William Tu wrote:
> On Fri, Feb 28, 2020 at 12:12 AM Ilya Maximets <i.maximets at ovn.org> wrote:
>>
>> On 2/27/20 8:52 PM, William Tu wrote:
>>> On Thu, Feb 27, 2020 at 11:10 AM William Tu <u9012063 at gmail.com> wrote:
>>>>
>>>> On Thu, Feb 27, 2020 at 9:54 AM Ilya Maximets <i.maximets at ovn.org> wrote:
>>>>>
>>>>> On 2/27/20 6:51 PM, William Tu wrote:
>>>>>> On Thu, Feb 27, 2020 at 9:42 AM Ilya Maximets <i.maximets at ovn.org> wrote:
>>>>>>>
>>>>>>> On 2/27/20 6:30 PM, William Tu wrote:
>>>>>>>> The patch adds a new netdev class 'afxdp-nonpmd' to enable afxdp
>>>>>>>> interrupt mode. This is similar to 'type=afxdp', except that the
>>>>>>>> is_pmd field is set to false. As a result, the packet processing
>>>>>>>> is handled by main thread, not pmd thread. This avoids burning
>>>>>>>> the CPU to always 100% when there is no traffic.
>>>>>>>>
>>>>>>>> Tested-at: https://travis-ci.org/williamtu/ovs-travis/builds/655885506
>>>>>>>> Signed-off-by: William Tu <u9012063 at gmail.com>
>>>>>>>> ---
>>>>>>>>  NEWS                  |  3 +++
>>>>>>>>  lib/netdev-afxdp.c    | 20 +++++++++++++++++++-
>>>>>>>>  lib/netdev-linux.c    | 20 ++++++++++++++++++++
>>>>>>>>  lib/netdev-provider.h |  1 +
>>>>>>>>  lib/netdev.c          |  1 +
>>>>>>>>  tests/system-afxdp.at | 23 +++++++++++++++++++++++
>>>>>>>>  6 files changed, 67 insertions(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/NEWS b/NEWS
>>>>>>>> index f62ef1f47ea8..594c55dc11d6 100644
>>>>>>>> --- a/NEWS
>>>>>>>> +++ b/NEWS
>>>>>>>> @@ -4,6 +4,9 @@ Post-v2.13.0
>>>>>>>>     - OpenFlow:
>>>>>>>>       * The OpenFlow ofp_desc/serial_num may now be configured by setting the
>>>>>>>>         value of other-config:dp-sn in the Bridge table.
>>>>>>>> +   - AF_XDP:
>>>>>>>> +     * New netdev class 'afxdp-nonpmd' for netdev-afxdp to save CPU cycles
>>>>>>>> +       by enabling interrupt mode.
>>>>>>>>
>>>>>>>>
>>>>>>>>  v2.13.0 - 14 Feb 2020
>>>>>>>> diff --git a/lib/netdev-afxdp.c b/lib/netdev-afxdp.c
>>>>>>>> index 482400d8d135..cd2c7c381139 100644
>>>>>>>> --- a/lib/netdev-afxdp.c
>>>>>>>> +++ b/lib/netdev-afxdp.c
>>>>>>>> @@ -169,6 +169,12 @@ struct netdev_afxdp_tx_lock {
>>>>>>>>      );
>>>>>>>>  };
>>>>>>>>
>>>>>>>> +static int nonpmd_cnt;  /* Number of afxdp netdevs in non-pmd mode. */
>>>>>>>> +static bool
>>>>>>>> +netdev_is_afxdp_nonpmd(struct netdev *netdev) {
>>>>>>>> +    return netdev_get_class(netdev) == &netdev_afxdp_nonpmd_class;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>>  #ifdef HAVE_XDP_NEED_WAKEUP
>>>>>>>>  static inline void
>>>>>>>>  xsk_rx_wakeup_if_needed(struct xsk_umem_info *umem,
>>>>>>>> @@ -1115,7 +1121,10 @@ netdev_afxdp_batch_send(struct netdev *netdev, int qid,
>>>>>>>>      struct netdev_linux *dev;
>>>>>>>>      int ret;
>>>>>>>>
>>>>>>>> -    if (concurrent_txq) {
>>>>>>>> +    /* Lock is required when mixing afxdp pmd and nonpmd mode.
>>>>>>>> +     * ex: one device is created 'afxdp', the other is 'afxdp-nonpmd'.
>>>>>>>> +     */
>>>>>>>> +    if (concurrent_txq || (nonpmd_cnt != 0)) {
>>>>>>>
>>>>>>> I'm confused about this change.  Are you expecting same device being
>>>>>>> opened twice with different netdev type?  Database should not allow this.
>>>>>>
>>>>>> Not the same device.
>>>>>>
>>>>>> For example, dev1 opened as 'afxdp', and dev2 opened as 'afxdp-nonpmd'.
>>>>>> When dev2 receives a packet and send to dev1, the main thread used by dev2
>>>>>> is calling the send(), while it is possible that dev2's pmd thread is
>>>>>> also calling
>>>>>> send(). So need a lock here.
>>>>>
>>>>> But they will send to different tx queues.
>>>>
>>>> OK,  I think you are talking about the XPS feature (dynamic txqs).
>>>> I thought XPS can only work when all between pmd threads.
>>>> So adding a lock here.
>>>> The patch currently doesn't work without the lock. Let me investigate more.
>>>>
>>> More details.
>>> On my test using veth (only have 1 rxq 1 txq)
>>> Somehow the main thread is assigned to use queue id  = 2, which causes segfault.
>>
>> That is very strange...
>> Could you, please, share your test setup?  I'll try to reproduce.
>>
>> Best regards, Ilya Maximets.
> 
> Sorry, somehow I miss your reply in my mailbox.
> I simply tested it using two namespaces, one device as afxdp, the
> other as afxdp-nonpmd.
> ---
> # start ovs-vswitchd and ovsdb-server
> 
> ovs-vsctl -- add-br br0 -- set Bridge br0 datapath_type=netdev
> ovs-vsctl set Open_vSwitch . other_config:pmd-cpu-mask=0xf
> 
> ip netns add at_ns0
> ip link add p0 type veth peer name afxdp-p0
> ip link set p0 netns at_ns0
> ip link set dev afxdp-p0 up
> ovs-vsctl add-port br0 afxdp-p0
> ovs-vsctl -- set interface afxdp-p0 options:n_rxq=1
> type="afxdp-nonpmd" options:xdp-mode=generic
> 
> ip netns exec at_ns0 sh << NS_EXEC_HEREDOC
> ip addr add "10.1.1.1/24" dev p0
> ip link set dev p0 up
> NS_EXEC_HEREDOC
> 
> ip netns add at_ns1
> ip link add p1 type veth peer name afxdp-p1
> ip link set p1 netns at_ns1
> ip link set dev afxdp-p1 up
> ovs-vsctl add-port br0 afxdp-p1 -- \
>                set interface afxdp-p1 type="afxdp"
> options:xdp-mode=generic options:n_rxq=1
> 
> ip netns exec at_ns1 sh << NS_EXEC_HEREDOC
> ip addr add "10.1.1.2/24" dev p1
> ip link set dev p1 up
> NS_EXEC_HEREDOC
> 
> ip netns exec at_ns0 ping  -c 10 -i .2 10.1.1.2
> ---
> 
> It's pretty easy to reproduce the issue, ping will crash the ovs-vswitchd.

Thanks.  I'll try to reproduce on next week.

Best regards, Ilya Maximets.


More information about the dev mailing list