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Björn Töpel says:
====================
Overview
========
Driver adoption for AF_XDP has been slow. The amount of code required
to proper support AF_XDP is substantial and the driver/core APIs are
vague or even non-existing. Drivers have to manually adjust data
offsets, updating AF_XDP handles differently for different modes
(aligned/unaligned).
This series attempts to improve the situation by introducing an AF_XDP
buffer allocation API. The implementation is based on a single core
(single producer/consumer) buffer pool for the AF_XDP UMEM.
A buffer is allocated using the xsk_buff_alloc() function, and
returned using xsk_buff_free(). If a buffer is disassociated with the
pool, e.g. when a buffer is passed to an AF_XDP socket, a buffer is
said to be released. Currently, the release function is only used by
the AF_XDP internals and not visible to the driver.
Drivers using this API should register the XDP memory model with the
new MEM_TYPE_XSK_BUFF_POOL type, which will supersede the
MEM_TYPE_ZERO_COPY type.
The buffer type is struct xdp_buff, and follows the lifetime of
regular xdp_buffs, i.e. the lifetime of an xdp_buff is restricted to
a NAPI context. In other words, the API is not replacing xdp_frames.
DMA mapping/synching is folded into the buffer handling as well.
@JeffK The Intel drivers changes should go through the bpf-next tree,
and not your regular Intel tree, since multiple (non-Intel)
drivers are affected.
The outline of the series is as following:
Patch 1 is a fix for xsk_umem_xdp_frame_sz().
Patch 2 to 4 are restructures/clean ups. The XSKMAP implementation is
moved to net/xdp/. Functions/defines/enums that are only used by the
AF_XDP internals are moved from the global include/net/xdp_sock.h to
net/xdp/xsk.h. We are also introducing a new "driver include file",
include/net/xdp_sock_drv.h, which is the only file NIC driver
developers adding AF_XDP zero-copy support should care about.
Patch 5 adds the new API, and migrates the "copy-mode"/skb-mode AF_XDP
path to the new API.
Patch 6 to 11 migrates the existing zero-copy drivers to the new API.
Patch 12 removes the MEM_TYPE_ZERO_COPY memory type, and the "handle"
member of struct xdp_buff.
Patch 13 simplifies the xdp_return_{frame,frame_rx_napi,buff}
functions.
Patch 14 is a performance patch, where some functions are inlined.
Finally, patch 15 updates the MAINTAINERS file to correctly mirror the
new file layout.
Note that this series removes the "handle" member from struct
xdp_buff, which reduces the xdp_buff size.
After this series, the diff stat of drivers/net/ is:
27 files changed, 419 insertions(+), 1288 deletions(-)
This series is a first step of simplifying the driver side of
AF_XDP. I think more of the AF_XDP logic can be moved from the drivers
to the AF_XDP core, e.g. the "need wakeup" set/clear functionality.
Statistics when allocation fails can now be added to the socket
statistics via the XDP_STATISTICS getsockopt(). This will be added in
a follow up series.
Performance
===========
As a nice side effect, performance is up a bit as well.
* i40e: 3% higher pps for rxdrop, zero-copy, aligned and unaligned
(40 GbE, 64B packets).
* mlx5: RX +0.8 Mpps, TX +0.4 Mpps
Changelog
=========
v4->v5:
* Fix various kdoc and GCC warnings (W=1). (Jakub)
v3->v4:
* mlx5: Remove unused variable num_xsk_frames. (Jakub)
* i40e: Made i40e_fd_handle_status() static. (kbuild test robot)
v2->v3:
* Added xsk_umem_xdp_frame_sz() fix to the series. (Björn)
* Initialize struct xdp_buff member frame_sz. (Björn)
* Add API to query the DMA address of a frame. (Maxim)
* Do DMA sync for CPU till the end of the frame to handle possible
growth (frame_sz). (Maxim)
* mlx5: Handle frame_sz, use xsk_buff_xdp_get_frame_dma, use
xsk_buff API for DMA sync on TX, add performance numbers. (Maxim)
v1->v2:
* mlx5: Fix DMA address handling, set XDP metadata to invalid. (Maxim)
* ixgbe: Fixed xdp_buff data_end update. (Björn)
* Swapped SoBs in patch 4. (Maxim)
rfc->v1:
* Fixed build errors/warnings for m68k and riscv. (kbuild test
robot)
* Added headroom/chunk size getter. (Maxim/Björn)
* mlx5: Put back the sanity check for XSK params, use XSK API to get
the total headroom size. (Maxim)
* Fixed spelling in commit message. (Björn)
* Make sure xp_validate_desc() is inlined for Tx perf. (Maxim)
* Sorted file entries. (Joe)
* Added xdp_return_{frame,frame_rx_napi,buff} simplification (Björn)
Thanks for all the comments/input/help!
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.