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David S. Miller 4629498336 Merge branch 'tcp-do-not-use-tcp_time_stamp-for-rcv-autotuning'
Eric Dumazet says:

====================
tcp: do not use tcp_time_stamp for rcv autotuning

Some devices or linux distributions use HZ=100 or HZ=250

TCP receive buffer autotuning has poor behavior caused by this choice.
Since autotuning happens after 4 ms or 10 ms, short distance flows
get their receive buffer tuned to a very high value, but after an initial
period where it was frozen to (too small) initial value.

With BBR (or other CC allowing to increase BDP), we are willing to
increase tcp_rmem[2], but this receive autotuning defect is a blocker
for hosts dealing with gazillions of TCP flows in the data centers,
since many of them have inflated RCVBUF. Risk of OOM is too high.

Note that TSO autodefer, tcp cubic, and TCP TS options (RFC 7323)
also suffer from our dependency to jiffies (via tcp_time_stamp).

We have ongoing efforts to improve all that in the future.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
History 2017-04-26 14:44:39 -04:00
arch sparc64: Improve 64-bit constant loading in eBPF JIT. 2017-04-24 20:32:15 -07:00
block blk-mq: fix potential oops with polling and blk-mq scheduler 2017-04-20 14:53:28 -06:00
certs certs: Add a secondary system keyring that can be added to dynamically 2016-04-11 22:48:09 +01:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-04-20 10:35:33 -04:00
Documentation net/tcp_fastopen: Disable active side TFO in certain scenarios 2017-04-24 14:27:17 -04:00
drivers drivers: net: xgene-v2: Fix error return code in xge_mdio_config() 2017-04-25 13:48:06 -04:00
firmware WHENCE: use https://linuxtv.org for LinuxTV URLs 2015-12-04 10:35:11 -02:00
fs Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-04-21 20:23:53 -07:00
include tcp: switch rcv_rtt_est and rcvq_space to high resolution timestamps 2017-04-26 14:44:39 -04:00
init mm: move mm_percpu_wq initialization earlier 2017-03-31 17:13:30 -07:00
ipc Merge branch 'WIP.sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-03 10:16:38 -08:00
kernel bpf: map_get_next_key to return first key on NULL 2017-04-25 11:57:45 -04:00
lib rhashtable: remove insecure_max_entries param 2017-04-26 14:39:24 -04:00
mm mm: prevent NR_ISOLATE_* stats from going negative 2017-04-20 15:30:18 -07:00
net tcp: switch rcv_rtt_est and rcvq_space to high resolution timestamps 2017-04-26 14:44:39 -04:00
samples samples/bpf: check before defining offsetof 2017-04-24 16:20:19 -04:00
scripts Kbuild fixes for v4.11 2017-04-05 08:37:28 -07:00
security Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-04-21 20:23:53 -07:00
sound ALSA: hda - fix a problem for lineout on a Dell AIO machine 2017-03-31 10:58:26 +02:00
tools bpf: map_get_next_key to return first key on NULL 2017-04-25 11:57:45 -04:00
usr kbuild: initramfs cleanup, set target from Kconfig 2017-01-05 09:40:16 -08:00
virt KVM/ARM Fixes for v4.11-rc6 2017-04-05 16:27:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Merge branch 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild 2016-08-02 16:48:52 -04:00
.mailmap mailmap: add Martin Kepplinger's email 2017-04-13 18:24:21 -07:00
COPYING [PATCH] update FSF address in COPYING 2005-09-10 10:06:29 -07:00
CREDITS MAINTAINERS: Remove old e-mail address 2017-02-13 12:24:56 -05:00
Kbuild scripts/gdb: provide linux constants 2016-05-23 17:04:14 -07:00
Kconfig kbuild: migrate all arch to the kconfig mainmenu upgrade 2010-09-19 22:54:11 -04:00
MAINTAINERS VSOCK: Add vsockmon device 2017-04-24 12:35:56 -04:00
Makefile Linux 4.11-rc7 2017-04-16 13:00:18 -07:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

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.