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Joshua Hay cb83b559be idpf: add support for Tx refillqs in flow scheduling mode
In certain production environments, it is possible for completion tags
to collide, meaning N packets with the same completion tag are in flight
at the same time. In this environment, any given Tx queue is effectively
used to send both slower traffic and higher throughput traffic
simultaneously. This is the result of a customer's specific
configuration in the device pipeline, the details of which Intel cannot
provide. This configuration results in a small number of out-of-order
completions, i.e., a small number of packets in flight. The existing
guardrails in the driver only protect against a large number of packets
in flight. The slower flow completions are delayed which causes the
out-of-order completions. The fast flow will continue sending traffic
and generating tags. Because tags are generated on the fly, the fast
flow eventually uses the same tag for a packet that is still in flight
from the slower flow. The driver has no idea which packet it should
clean when it processes the completion with that tag, but it will look
for the packet on the buffer ring before the hash table.  If the slower
flow packet completion is processed first, it will end up cleaning the
fast flow packet on the ring prematurely. This leaves the descriptor
ring in a bad state resulting in a crash or Tx timeout.

In summary, generating a tag when a packet is sent can lead to the same
tag being associated with multiple packets. This can lead to resource
leaks, crashes, and/or Tx timeouts.

Before we can replace the tag generation, we need a new mechanism for
the send path to know what tag to use next. The driver will allocate and
initialize a refillq for each TxQ with all of the possible free tag
values. During send, the driver grabs the next free tag from the refillq
from next_to_clean. While cleaning the packet, the clean routine posts
the tag back to the refillq's next_to_use to indicate that it is now
free to use.

This mechanism works exactly the same way as the existing Rx refill
queues, which post the cleaned buffer IDs back to the buffer queue to be
reposted to HW. Since we're using the refillqs for both Rx and Tx now,
genericize some of the existing refillq support.

Note: the refillqs will not be used yet. This is only demonstrating how
they will be used to pass free tags back to the send path.

Signed-off-by: Joshua Hay <joshua.a.hay@intel.com>
Reviewed-by: Madhu Chittim <madhu.chittim@intel.com>
Tested-by: Samuel Salin <Samuel.salin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
2025-08-21 09:04:58 -07:00
arch Including fixes from Netfilter and IPsec. 2025-08-14 07:14:30 -07:00
block block-6.17-20250808 2025-08-09 08:47:28 +03:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
Documentation mptcp: disable add_addr retransmission when timeout is 0 2025-08-18 17:39:58 -07:00
drivers idpf: add support for Tx refillqs in flow scheduling mode 2025-08-21 09:04:58 -07:00
fs Changes since last update: 2025-08-13 11:29:27 -07:00
include bonding: update LACP activity flag after setting lacp_active 2025-08-21 09:35:20 +02:00
init Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
io_uring io_uring/memmap: cast nr_pages to size_t before shifting 2025-08-08 06:35:14 -06:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel Including fixes from Netfilter and IPsec. 2025-08-14 07:14:30 -07:00
lib Including fixes from Netfilter and IPsec. 2025-08-14 07:14:30 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm/mremap: avoid expensive folio lookup on mremap folio pte batch 2025-08-11 23:00:59 -07:00
net tls: fix handling of zero-length records on the rx_list 2025-08-21 07:52:30 -07:00
rust Rust changes for v6.17 2025-08-03 13:49:10 -07:00
samples Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
scripts Kbuild updates for v6.17 2025-08-06 07:32:52 +03:00
security + Features 2025-08-04 08:17:28 -07:00
sound gpio updates for v6.17-rc1 2025-08-09 08:15:43 +03:00
tools selftests: tls: add tests for zero-length records 2025-08-21 07:52:31 -07:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore gitignore: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS Kbuild updates for v6.17 2025-08-06 07:32:52 +03:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS MAINTAINERS: update s390/net 2025-08-14 17:36:15 -07:00
Makefile Linux 6.17-rc1 2025-08-10 19:41:16 +03:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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 reStructuredText 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.