Date:   Mon, 24 Jun 2019 17:38:33 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Kevin Laatz <kevin.laatz@...el.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        bpf@...r.kernel.com,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        Bruce Richardson <bruce.richardson@...el.com>,
        ciara.loftus@...el.com
Subject: Re: [PATCH 00/11] XDP unaligned chunk placement support

On Thu, 20 Jun 2019 at 18:55, Kevin Laatz <kevin.laatz@...el.com> wrote:
>
> This patchset adds the ability to use unaligned chunks in the XDP umem.
>
> Currently, all chunk addresses passed to the umem are masked to be chunk
> size aligned (default is 2k, max is PAGE_SIZE). This limits where we can
> place chunks within the umem as well as limiting the packet sizes that are
> supported.
>
> The changes in this patchset removes these restrictions, allowing XDP to be
> more flexible in where it can place a chunk within a umem. By relaxing where
> the chunks can be placed, it allows us to use an arbitrary buffer size and
> place that wherever we have a free address in the umem. These changes add the
> ability to support jumboframes and make it easy to integrate with other
> existing frameworks that have their own memory management systems, such as
> DPDK.
>

Thanks for working on this, Kevin and Ciara!

I have some minor comments on the series, but in general I think it's
in good shape!

For some reason the series was submitted twice (at least on my side)?


Thanks,
Björn

> Structure of the patchset:
> Patch 1:
>   - Remove unnecessary masking and headroom addition during zero-copy Rx
>     buffer recycling in i40e. This change is required in order for the
>     buffer recycling to work in the unaligned chunk mode.
>
> Patch 2:
>   - Remove unnecessary masking and headroom addition during
>     zero-copy Rx buffer recycling in ixgbe. This change is required in
>     order for the  buffer recycling to work in the unaligned chunk mode.
>
> Patch 3:
>   - Adds an offset parameter to zero_copy_allocator. This change will
>     enable us to calculate the original handle in zca_free. This will be
>     required for unaligned chunk mode since we can't easily mask back to
>     the original handle.
>
> Patch 4:
>   - Adds the offset parameter to i40e_zca_free. This change is needed for
>     calculating the handle since we can't easily mask back to the original
>     handle like we can in the aligned case.
>
> Patch 5:
>   - Adds the offset parameter to ixgbe_zca_free. This change is needed for
>     calculating the handle since we can't easily mask back to the original
>     handle like we can in the aligned case.
>
>
> Patch 6:
>   - Add infrastructure for unaligned chunks. Since we are dealing
>     with unaligned chunks that could potentially cross a physical page
>     boundary, we add checks to keep track of that information. We can
>     later use this information to correctly handle buffers that are
>     placed at an address where they cross a page boundary.
>
> Patch 7:
>   - Add flags for umem configuration to libbpf
>
> Patch 8:
>   - Modify xdpsock application to add a command line option for
>     unaligned chunks
>
> Patch 9:
>   - Addition of command line argument to pass in a desired buffer size
>     and buffer recycling for unaligned mode. Passing in a buffer size will
>     allow the application to use unaligned chunks with the unaligned chunk
>     mode. Since we are now using unaligned chunks, we need to recycle our
>     buffers in a slightly different way.
>
> Patch 10:
>   - Adds hugepage support to the xdpsock application
>
> Patch 11:
>   - Documentation update to include the unaligned chunk scenario. We need
>     to explicitly state that the incoming addresses are only masked in the
>     aligned chunk mode and not the unaligned chunk mode.
>
> Kevin Laatz (11):
>   i40e: simplify Rx buffer recycle
>   ixgbe: simplify Rx buffer recycle
>   xdp: add offset param to zero_copy_allocator
>   i40e: add offset to zca_free
>   ixgbe: add offset to zca_free
>   xsk: add support to allow unaligned chunk placement
>   libbpf: add flags to umem config
>   samples/bpf: add unaligned chunks mode support to xdpsock
>   samples/bpf: add buffer recycling for unaligned chunks to xdpsock
>   samples/bpf: use hugepages in xdpsock app
>   doc/af_xdp: include unaligned chunk case
>
>  Documentation/networking/af_xdp.rst           | 10 +-
>  drivers/net/ethernet/intel/i40e/i40e_xsk.c    | 21 ++--
>  drivers/net/ethernet/intel/i40e/i40e_xsk.h    |  3 +-
>  .../ethernet/intel/ixgbe/ixgbe_txrx_common.h  |  3 +-
>  drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c  | 21 ++--
>  include/net/xdp.h                             |  3 +-
>  include/net/xdp_sock.h                        |  2 +
>  include/uapi/linux/if_xdp.h                   |  4 +
>  net/core/xdp.c                                | 11 ++-
>  net/xdp/xdp_umem.c                            | 17 ++--
>  net/xdp/xsk.c                                 | 60 +++++++++--
>  net/xdp/xsk_queue.h                           | 60 +++++++++--
>  samples/bpf/xdpsock_user.c                    | 99 ++++++++++++++-----
>  tools/include/uapi/linux/if_xdp.h             |  4 +
>  tools/lib/bpf/xsk.c                           |  7 ++
>  tools/lib/bpf/xsk.h                           |  2 +
>  16 files changed, 241 insertions(+), 86 deletions(-)
>
> --
> 2.17.1
>

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