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Filename Latest commit message Latest commit date
Alexey Dobriyan 4c6080cd6f lib/list: tweak LIST_POISON2 for better code generation on x86_64
list_del() poisoning can generate 2 64-bit immediate loads but it also can
generate one 64-bit immediate load and an addition:

	48 b8 00 01 00 00 00 00 ad de	movabs rax,0xdead000000000100
	48 89 47 58			mov    QWORD PTR [rdi+0x58],rax
	48 05 00 01 00 00   <=====>	add    rax,0x100
	48 89 47 60			mov    QWORD PTR [rdi+0x60],rax

However on x86_64 not all constants are equal: those within [-128, 127]
range can be added with shorter "add r64, imm32" instruction:

	48 b8 00 01 00 00 00 00 ad de	movabs rax,0xdead000000000100
	48 89 47 58			mov    QWORD PTR [rdi+0x58],rax
	48 83 c0 22	<======>	add    rax,0x22
	48 89 47 60			mov    QWORD PTR [rdi+0x60],rax

Patch saves 2 bytes per some LIST_POISON2 usage.

(Slightly disappointing) space savings on F29 x86_64 config:

	add/remove: 0/0 grow/shrink: 0/2164 up/down: 0/-5184 (-5184)
	Function                                     old     new   delta
	zstd_get_workspace                           548     546      -2
		...
	mlx4_delete_all_resources_for_slave         4826    4804     -22
	Total: Before=83304131, After=83298947, chg -0.01%

New constants are:

	0xdead000000000100
	0xdead000000000122

Note: LIST_POISON1 can't be changed to ...11 because something in page
allocator requires low bit unset.

Link: http://lkml.kernel.org/r/20190513191502.GA8492@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-16 19:23:22 -07:00
arch arch/*: remove unused isa_page_to_bus() 2019-07-16 19:23:22 -07:00
block
certs
crypto
Documentation kernel: fix typos and some coding style in comments 2019-07-16 19:23:21 -07:00
drivers kernel: fix typos and some coding style in comments 2019-07-16 19:23:21 -07:00
fs fs/proc/proc_sysctl.c: fix the default values of i_uid/i_gid on /proc/sys inodes. 2019-07-16 19:23:21 -07:00
include lib/list: tweak LIST_POISON2 for better code generation on x86_64 2019-07-16 19:23:22 -07:00
init
ipc
kernel kernel: fix typos and some coding style in comments 2019-07-16 19:23:21 -07:00
lib
LICENSES
mm
net
samples
scripts get_maintainer: add ability to skip moderated mailing lists 2019-07-16 19:23:22 -07:00
security
sound kernel: fix typos and some coding style in comments 2019-07-16 19:23:21 -07:00
tools
usr
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.cocciconfig
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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.