Re: [PATCH v2 0/5] Introducing ixgbe AF_XDP ZC support

["Björn Töpel" <bjorn.topel@intel.com>]

On 2018-10-02 20:23, William Tu wrote:
> On Tue, Oct 2, 2018 at 1:01 AM Björn Töpel <bjorn.topel@gmail.com> wrote:
>>
>> From: Björn Töpel <bjorn.topel@intel.com>
>>
>> Jeff: Please remove the v1 patches from your dev-queue!
>>
>> This patch set introduces zero-copy AF_XDP support for Intel's ixgbe
>> driver.
>>
>> The ixgbe zero-copy code is located in its own file ixgbe_xsk.[ch],
>> analogous to the i40e ZC support. Again, as in i40e, code paths have
>> been copied from the XDP path to the zero-copy path. Going forward we
>> will try to generalize more code between the AF_XDP ZC drivers, and
>> also reduce the heavy C&P.
>>
>> We have run some benchmarks on a dual socket system with two Broadwell
>> E5 2660 @ 2.0 GHz with hyperthreading turned off. Each socket has 14
>> cores which gives a total of 28, but only two cores are used in these
>> experiments. One for TR/RX and one for the user space application. The
>> memory is DDR4 @ 2133 MT/s (1067 MHz) and the size of each DIMM is
>> 8192MB and with 8 of those DIMMs in the system we have 64 GB of total
>> memory. The compiler used is GCC 7.3.0. The NIC is Intel
>> 82599ES/X520-2 10Gbit/s using the ixgbe driver.
>>
>> Below are the results in Mpps of the 82599ES/X520-2 NIC benchmark runs
>> for 64B and 1500B packets, generated by a commercial packet generator
>> HW blasting packets at full 10Gbit/s line rate. The results are with
>> retpoline and all other spectre and meltdown fixes.
>>
>> AF_XDP performance 64B packets:
>> Benchmark   XDP_DRV with zerocopy
>> rxdrop        14.7
>> txpush        14.6
>> l2fwd         11.1
>>
>> AF_XDP performance 1500B packets:
>> Benchmark   XDP_DRV with zerocopy
>> rxdrop        0.8
>> l2fwd         0.8
>>
>> XDP performance on our system as a base line.
>>
>> 64B packets:
>> XDP stats       CPU     Mpps       issue-pps
>> XDP-RX CPU      16      14.7       0
>>
>> 1500B packets:
>> XDP stats       CPU     Mpps       issue-pps
>> XDP-RX CPU      16      0.8        0
>>
>> The structure of the patch set is as follows:
>>
>> Patch 1: Introduce Rx/Tx ring enable/disable functionality
>> Patch 2: Preparatory patche to ixgbe driver code for RX
>> Patch 3: ixgbe zero-copy support for RX
>> Patch 4: Preparatory patch to ixgbe driver code for TX
>> Patch 5: ixgbe zero-copy support for TX
>>
>> Changes since v1:
>>
>> * Removed redundant AF_XDP precondition checks, pointed out by
>>    Jakub. Now, the preconditions are only checked at XDP enable time.
>> * Fixed a crash in the egress path, due to incorrect usage of
>>    ixgbe_ring queue_index member. In v2 a ring_idx back reference is
>>    introduced, and used in favor of queue_index. William reported the
>>    crash, and helped me smoke out the issue. Kudos!
> 
> Thanks! I tested this series and no more crash.

Thank you for spending time on this!

> The number is pretty good (*without* spectre and meltdown fixes)
> model name : Intel(R) Xeon(R) CPU E5-2440 v2 @ 1.90GHz, total 16 cores/
> 
> AF_XDP performance 64B packets:
> Benchmark   XDP_DRV with zerocopy
> rxdrop        20
> txpush        18
> l2fwd         20
>

What is 20 here? Given that 14.8Mpps is maximum for 64B@10Gbit/s for
one queue, is this multiple queues? Is this xdpsock or OvS with AF_XDP?


Cheers,
Björn

> Regards,
> William
>