Johnathan, Bjorn, Jakub, Please review! The patch set has been pending for a week. On Tue, Jul 16, 2019 at 4:21 AM Kevin Laatz <kevin.laatz@xxxxxxxxx> wrote: > > This patch set 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 patch set 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 arbitrary frame sizes up to 4k > (PAGE_SIZE) and make it easy to integrate with other existing frameworks > that have their own memory management systems, such as DPDK. > > Since we are now dealing with arbitrary frame sizes, we need also need to > update how we pass around addresses. Currently, the addresses can simply be > masked to 2k to get back to the original address. This becomes less trivial > when using frame sizes that are not a 'power of 2' size. This patch set > modifies the Rx/Tx descriptor format to use the upper 16-bits of the addr > field for an offset value, leaving the lower 48-bits for the address (this > leaves us with 256 Terabytes, which should be enough!). We only need to use > the upper 16-bits to store the offset when running in unaligned mode. > Rather than adding the offset (headroom etc) to the address, we will store > it in the upper 16-bits of the address field. This way, we can easily add > the offset to the address where we need it, using some bit manipulation and > addition, and we can also easily get the original address wherever we need > it (for example in i40e_zca_free) by simply masking to get the lower > 48-bits of the address field. > > The numbers below were recorded with the following set up: > - Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz > - Intel Corporation Ethernet Controller XXV710 for 25GbE SFP28 (rev 02) > - Driver: i40e > - Application: xdpsock with l2fwd (single interface) > > These are solely for comparing performance with and without the patches. > The largest drop was ~1% (in zero-copy mode). > > +-------------------------+------------+-----------------+-------------+ > | Buffer size: 2048 | SKB mode | Zero-copy | Copy | > +-------------------------+------------+-----------------+-------------+ > | Aligned (baseline) | 1.7 Mpps | 15.3 Mpps | 2.08 Mpps | > +-------------------------+------------+-----------------+-------------+ > | Aligned (with patches) | 1.7 Mpps | 15.1 Mpps | 2.08 Mpps | > +-------------------------+------------+-----------------+-------------+ > | Unaligned | 1.7 Mpps | 14.5 Mpps | 2.08 Mpps | > +-------------------------+------------+-----------------+-------------+ > > NOTE: We are currently working on the changes required in the Mellanox > driver. We will include these in the v3. > > 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: > - 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. This patch also modifies the > existing Rx and Tx functions to use the new descriptor format. To > handle addresses correctly, we need to mask appropriately based on > whether we are in aligned or unaligned mode. > > Patch 4: > - This patch updates the i40e driver to make use of the new descriptor > format. The new format is particularly useful here since we can now > retrieve the original address in places like i40e_zca_free with ease. > This saves us doing various calculations to get the original address > back. > > Patch 5: > - This patch updates the ixgbe driver to make use of the new descriptor > format. The new format is particularly useful here since we can now > retrieve the original address in places like ixgbe_zca_free with ease. > This saves us doing various calculations to get the original address > back. > > Patch 6: > - Add flags for umem configuration to libbpf > > Patch 7: > - Modify xdpsock application to add a command line option for > unaligned chunks > > Patch 8: > - Since we can now run the application in unaligned chunk mode, we need > to make sure we recycle the buffers appropriately. > > Patch 9: > - Adds hugepage support to the xdpsock application > > Patch 10: > - 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. > > --- > v2: > - fixed checkpatch issues > - fixed Rx buffer recycling for unaligned chunks in xdpsock > - removed unused defines > - fixed how chunk_size is calculated in xsk_diag.c > - added some performance numbers to cover letter > - modified descriptor format to make it easier to retrieve original > address > - removed patch adding off_t off to the zero copy allocator. This is no > longer needed with the new descriptor format. > > Kevin Laatz (10): > i40e: simplify Rx buffer recycle > ixgbe: simplify Rx buffer recycle > xsk: add support to allow unaligned chunk placement > i40e: modify driver for handling offsets > ixgbe: modify driver for handling offsets > 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 | 39 +++++---- > drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 39 +++++---- > include/net/xdp_sock.h | 2 + > include/uapi/linux/if_xdp.h | 9 ++ > net/xdp/xdp_umem.c | 17 ++-- > net/xdp/xsk.c | 89 ++++++++++++++++---- > net/xdp/xsk_diag.c | 2 +- > net/xdp/xsk_queue.h | 70 +++++++++++++-- > samples/bpf/xdpsock_user.c | 61 ++++++++++---- > tools/include/uapi/linux/if_xdp.h | 4 + > tools/lib/bpf/xsk.c | 3 + > tools/lib/bpf/xsk.h | 2 + > 13 files changed, 266 insertions(+), 81 deletions(-) > > -- > 2.17.1 >
