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Eric Dumazet d6a76199e8 tcp_bbr: better deal with suboptimal GSO 
[ Upstream commit 350c9f484b ]

BBR uses tcp_tso_autosize() in an attempt to probe what would be the
burst sizes and to adjust cwnd in bbr_target_cwnd() with following
gold formula :

/* Allow enough full-sized skbs in flight to utilize end systems. */
cwnd += 3 * bbr->tso_segs_goal;

But GSO can be lacking or be constrained to very small
units (ip link set dev ... gso_max_segs 2)

What we really want is to have enough packets in flight so that both
GSO and GRO are efficient.

So in the case GSO is off or downgraded, we still want to have the same
number of packets in flight as if GSO/TSO was fully operational, so
that GRO can hopefully be working efficiently.

To fix this issue, we make tcp_tso_autosize() unaware of
sk->sk_gso_max_segs

Only tcp_tso_segs() has to enforce the gso_max_segs limit.

Tested:

ethtool -K eth0 tso off gso off
tc qd replace dev eth0 root pfifo_fast

Before patch:
for f in {1..5}; do ./super_netperf 1 -H lpaa24 -- -K bbr; done
    691  (ss -temoi shows cwnd is stuck around 6 )
    667
    651
    631
    517

After patch :
# for f in {1..5}; do ./super_netperf 1 -H lpaa24 -- -K bbr; done
   1733 (ss -temoi shows cwnd is around 386 )
   1778
   1746
   1781
   1718

Fixes: 0f8782ea14 ("tcp_bbr: add BBR congestion control")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-03-08 22:41:13 -08:00
arch x86/cpu_entry_area: Sync cpu_entry_area to initial_page_table 2018-03-08 22:41:07 -08:00
block block: kyber: fix domain token leak during requeue 2018-03-08 22:41:05 -08:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto crypto: af_alg - Fix race around ctx->rcvused by making it atomic_t 2018-03-03 10:24:29 +01:00
Documentation ext4: correct documentation for grpid mount option 2018-02-22 15:42:26 +01:00
drivers net: phy: fix phy_start to consider PHY_IGNORE_INTERRUPT 2018-03-08 22:41:12 -08:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs direct-io: Fix sleep in atomic due to sync AIO 2018-03-08 22:41:06 -08:00
include udplite: fix partial checksum initialization 2018-03-08 22:41:10 -08:00
init kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK 2018-02-22 15:42:23 +01:00
ipc License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kernel timers: Forward timer base before migrating timers 2018-03-08 22:41:04 -08:00
lib lib/mpi: Fix umul_ppmm() for MIPS64r6 2018-03-03 10:24:29 +01:00
mm mm/frame_vector.c: release a semaphore in 'get_vaddr_frames()' 2018-03-03 10:24:21 +01:00
net tcp_bbr: better deal with suboptimal GSO 2018-03-08 22:41:13 -08:00
samples samples/bpf: adjust rlimit RLIMIT_MEMLOCK for xdp1 2017-12-20 10:10:31 +01:00
scripts scripts/kernel-doc: Don't fail with status != 0 if error encountered with -none 2018-02-25 11:07:58 +01:00
security selinux: skip bounded transition processing if the policy isn't loaded 2018-02-25 11:07:49 +01:00
sound ALSA: hda - Fix pincfg at resume on Lenovo T470 dock 2018-03-08 22:41:02 -08:00
tools perf test: Fix test 21 for s390x 2018-02-25 11:07:55 +01:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: Fix spinlock acquisition in vgic_set_owner 2018-02-25 11:07:56 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS kmemcheck: rip it out 2018-02-22 15:42:24 +01:00
Makefile Linux 4.14.24 2018-03-03 10:24:39 +01:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.