On 20 Jun 2019, at 1:39, Kevin Laatz 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.
I'm a little unclear on how this should work, and have a few issues
here:
1) There isn't any support for the user defined umem->headroom
2) When queuing RX buffers, the handle (aka umem offset) is used,
which
points to the start of the buffer area. When the buffer appears in
the completion queue, handle points to the start of the received
data,
which might be different from the buffer start address.
Normally, this RX address is just put back in the fill queue, and
the
mask is used to find the buffer start address again. This no
longer
works, so my question is, how is the buffer start address
recomputed
from the actual data payload address?
Same with TX - if the TX payload isn't aligned in with the start of
the buffer, what happens?
3) This appears limited to crossing a single page boundary, but there
is no constraint check on chunk_size.
--
Jonathan
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
