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Paolo Abeni 9e8445a56c net: avoid unneeded atomic operation in ip*_append_data() 
After commit 694aba690d ("ipv4: factorize sk_wmem_alloc updates
done by __ip_append_data()") and commit 1f4c6eb240 ("ipv6:
factorize sk_wmem_alloc updates done by __ip6_append_data()"),
when transmitting sub MTU datagram, an addtional, unneeded atomic
operation is performed in ip*_append_data() to update wmem_alloc:
in the above condition the delta is 0.

The above cause small but measurable performance regression in UDP
xmit tput test with packet size below MTU.

This change avoids such overhead updating wmem_alloc only if
wmem_alloc_delta is non zero.

The error path is left intentionally unmodified: it's a slow path
and simplicity is preferred to performances.

Fixes: 694aba690d ("ipv4: factorize sk_wmem_alloc updates done by __ip_append_data()")
Fixes: 1f4c6eb240 ("ipv6: factorize sk_wmem_alloc updates done by __ip6_append_data()")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2018-04-04 11:53:08 -04:00
Documentation Merge branch 'for-4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata 2018-04-03 17:42:25 -07:00
LICENSES LICENSES: Add MPL-1.1 license 2018-01-06 10:59:44 -07:00
arch media updates for v4.17-rc1 2018-04-03 17:16:59 -07:00
block treewide: simplify Kconfig dependencies for removed archs 2018-03-26 15:55:57 +02:00
certs certs/blacklist_nohashes.c: fix const confusion in certs blacklist 2018-02-21 15:35:43 -08:00
crypto mn10300: Remove the architecture 2018-03-09 23:19:56 +01:00
drivers nvmem: disallow modular CONFIG_NVMEM 2018-04-04 11:47:50 -04:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Merge branch 'for-4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2018-04-03 18:00:13 -07:00
include ipv6: allow to cache dst for a connected sk in ip6_sk_dst_lookup_flow() 2018-04-04 11:31:57 -04:00
init Merge branch 'syscalls-next' of git://git.kernel.org/pub/scm/linux/kernel/git/brodo/linux 2018-04-02 21:22:12 -07:00
ipc Merge branch 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2018-04-03 19:15:32 -07:00
kernel Merge branch 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2018-04-03 19:15:32 -07:00
lib Kbuild updates for v4.17 2018-04-03 15:51:22 -07:00
mm Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-next 2018-04-03 14:08:58 -07:00
net net: avoid unneeded atomic operation in ip*_append_data() 2018-04-04 11:53:08 -04:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-04-03 14:04:18 -07:00
scripts Kconfig updates for v4.17 2018-04-03 16:28:01 -07:00
security Merge branch 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2018-04-03 19:15:32 -07:00
sound Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-04-03 14:04:18 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-04-03 14:04:18 -07:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt kvm/arm fixes for 4.16, take 2 2018-03-15 21:45:37 +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: move include/config/ksym/* to include/ksym/* 2018-03-26 02:01:23 +09:00
.mailmap Merge remote-tracking branch 'spi/topic/samsung' into spi-next 2018-04-02 15:56:32 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS/CREDITS: Drop METAG ARCHITECTURE 2018-03-05 16:34:24 +00:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS media updates for v4.17-rc1 2018-04-03 17:16:59 -07:00
Makefile Kconfig updates for v4.17 2018-04-03 16:28:01 -07:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -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.
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.