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Neal Cardwell 821b3b00bc tcp: fix quick-ack counting to count actual ACKs of new data
[ Upstream commit 059217c18b ]

This commit fixes quick-ack counting so that it only considers that a
quick-ack has been provided if we are sending an ACK that newly
acknowledges data.

The code was erroneously using the number of data segments in outgoing
skbs when deciding how many quick-ack credits to remove. This logic
does not make sense, and could cause poor performance in
request-response workloads, like RPC traffic, where requests or
responses can be multi-segment skbs.

When a TCP connection decides to send N quick-acks, that is to
accelerate the cwnd growth of the congestion control module
controlling the remote endpoint of the TCP connection. That quick-ack
decision is purely about the incoming data and outgoing ACKs. It has
nothing to do with the outgoing data or the size of outgoing data.

And in particular, an ACK only serves the intended purpose of allowing
the remote congestion control to grow the congestion window quickly if
the ACK is ACKing or SACKing new data.

The fix is simple: only count packets as serving the goal of the
quickack mechanism if they are ACKing/SACKing new data. We can tell
whether this is the case by checking inet_csk_ack_scheduled(), since
we schedule an ACK exactly when we are ACKing/SACKing new data.

Fixes: fc6415bcb0 ("[TCP]: Fix quick-ack decrementing with TSO.")
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231001151239.1866845-1-ncardwell.sw@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-10-10 21:59:08 +02:00
Documentation perf/smmuv3: Enable HiSilicon Erratum 162001900 quirk for HIP08/09 2023-09-23 11:09:55 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
arch arm64: Add Cortex-A520 CPU part definition 2023-10-10 21:59:06 +02:00
block block: fix use-after-free of q->q_usage_counter 2023-10-10 21:59:05 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: lrw,xts - Replace strlcpy with strscpy 2023-09-23 11:09:55 +02:00
drivers net: stmmac: dwmac-stm32: fix resume on STM32 MCU 2023-10-10 21:59:08 +02:00
fs NFSv4: Fix a nfs4_state_manager() race 2023-10-10 21:59:07 +02:00
include tcp: fix quick-ack counting to count actual ACKs of new data 2023-10-10 21:59:08 +02:00
init x86/mm: Initialize text poking earlier 2023-08-08 19:58:33 +02:00
io_uring io_uring/fs: remove sqe->rw_flags checking from LINKAT 2023-10-06 13:18:22 +02:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel ring-buffer: Fix bytes info in per_cpu buffer stats 2023-10-10 21:59:05 +02:00
lib kobject: Add sanity check for kset->kobj.ktype in kset_register() 2023-09-23 11:09:59 +02:00
mm mm/vmalloc: add a safer version of find_vm_area() for debug 2023-09-19 12:22:50 +02:00
net tcp: fix quick-ack counting to count actual ACKs of new data 2023-10-10 21:59:08 +02:00
samples samples/hw_breakpoint: fix building without module unloading 2023-09-23 11:10:01 +02:00
scripts modpost: add missing else to the "of" check 2023-10-10 21:59:07 +02:00
security ima: rework CONFIG_IMA dependency block 2023-10-10 21:59:07 +02:00
sound ASoC: tegra: Fix redundant PLLA and PLLA_OUT0 updates 2023-10-10 21:59:04 +02:00
tools bpf: Fix BTF_ID symbol generation collision in tools/ 2023-10-06 13:18:23 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: Grab a reference to KVM for VM and vCPU stats file descriptors 2023-08-03 10:22:40 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS iio: stx104: Move to addac subdirectory 2023-08-26 14:23:27 +02:00
Makefile Linux 5.15.134 2023-10-06 13:18:24 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.