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Eric Dumazet ce27ec6064 net: add high_order_alloc_disable sysctl/static key 
>From linux-3.7, (commit 5640f76858 "net: use a per task frag
allocator") TCP sendmsg() has preferred using order-3 allocations.

While it gives good results for most cases, we had reports
that heavy uses of TCP over loopback were hitting a spinlock
contention in page allocations/freeing.

This commits adds a sysctl so that admins can opt-in
for order-0 allocations. Hopefully mm layer might optimize
order-3 allocations in the future since it could give us
a nice boost  (see 8 lines of following benchmark)

The following benchmark shows a win when more than 8 TCP_STREAM
threads are running (56 x86 cores server in my tests)

for thr in {1..30}
do
 sysctl -wq net.core.high_order_alloc_disable=0
 T0=`./super_netperf $thr -H 127.0.0.1 -l 15`
 sysctl -wq net.core.high_order_alloc_disable=1
 T1=`./super_netperf $thr -H 127.0.0.1 -l 15`
 echo $thr:$T0:$T1
done

1: 49979: 37267
2: 98745: 76286
3: 141088: 110051
4: 177414: 144772
5: 197587: 173563
6: 215377: 208448
7: 241061: 234087
8: 267155: 263373
9: 295069: 297402
10: 312393: 335213
11: 340462: 368778
12: 371366: 403954
13: 412344: 443713
14: 426617: 473580
15: 474418: 507861
16: 503261: 538539
17: 522331: 563096
18: 532409: 567084
19: 550824: 605240
20: 525493: 641988
21: 564574: 665843
22: 567349: 690868
23: 583846: 710917
24: 588715: 736306
25: 603212: 763494
26: 604083: 792654
27: 602241: 796450
28: 604291: 797993
29: 611610: 833249
30: 577356: 841062

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2019-06-14 20:18:28 -07:00
Documentation tcp: add tcp_rx_skb_cache sysctl 2019-06-14 20:18:28 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2019-06-07 14:46:47 -07:00
block block: print offending values when cloned rq limits are exceeded 2019-05-31 15:12:34 -06:00
certs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2019-06-06 13:10:49 -07:00
drivers hv_netvsc: Set probe mode to sync 2019-06-14 19:47:05 -07:00
fs Changes since last update: 2019-06-06 12:36:54 -07:00
include net: add high_order_alloc_disable sysctl/static key 2019-06-14 20:18:28 -07:00
init treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 167 2019-05-30 11:26:39 -07:00
ipc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 52 2019-05-24 17:36:42 +02:00
kernel sysctl: define proc_do_static_key() 2019-06-14 20:18:27 -07:00
lib SPDX fixes for 5.2-rc3, round 2 2019-06-02 10:22:38 -07:00
mm mm, compaction: make sure we isolate a valid PFN 2019-06-01 15:51:32 -07:00
net net: add high_order_alloc_disable sysctl/static key 2019-06-14 20:18:28 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2019-06-07 14:46:47 -07:00
scripts Merge branch 'akpm' (patches from Andrew) 2019-06-02 08:51:30 -07:00
security Merge branch 'next-fixes-for-5.2-rc' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity 2019-05-31 11:08:44 -07:00
sound treewide: fix typos of SPDX-License-Identifier 2019-06-01 18:29:58 +02:00
tools selftests: tc_flower: Add TOS matching test 2019-06-12 11:08:14 -07:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt Fixes for PPC and s390. 2019-06-02 10:19:39 -07:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.cocciconfig
…
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes
…
.gitignore .gitignore: exclude .get_maintainer.ignore and .gitattributes 2019-05-18 11:49:54 +09:00
.mailmap A reasonably busy cycle for docs, including: 2019-05-08 12:42:50 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Farewell Martin Schwidefsky 2019-05-31 10:14:11 +02:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-06-07 09:29:14 -07:00
Makefile Linux 5.2-rc3 2019-06-02 13:55:33 -07:00
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.