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

Ilya Maximets i.maximets at ovn.org
Thu Feb 27 17:54:38 UTC 2020


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.


More information about the dev mailing list