github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-07-28 10:09:10 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph
Linux kernel source tree
948,990 Commits 1 Branch 940 Tags 24 GiB
C 96.9%
Assembly 0.9%
Rust 0.6%
Shell 0.6%
Python 0.5%
Other 0.3%
394b19d6cb
Go to file
Arvind Sankar 394b19d6cb x86/boot/compressed: Use builtin mem functions for decompressor 
Since commits

  c041b5ad86 ("x86, boot: Create a separate string.h file to provide standard string functions")
  fb4cac573e ("x86, boot: Move memcmp() into string.h and string.c")

the decompressor stub has been using the compiler's builtin memcpy,
memset and memcmp functions, _except_ where it would likely have the
largest impact, in the decompression code itself.

Remove the #undef's of memcpy and memset in misc.c so that the
decompressor code also uses the compiler builtins.

The rationale given in the comment doesn't really apply: just because
some functions use the out-of-line version is no reason to not use the
builtin version in the rest.

Replace the comment with an explanation of why memzero and memmove are
being #define'd.

Drop the suggestion to #undef in boot/string.h as well: the out-of-line
versions are not really optimized versions, they're generic code that's
good enough for the preboot environment. The compiler will likely
generate better code for constant-size memcpy/memset/memcmp if it is
allowed to.

Most decompressors' performance is unchanged, with the exception of LZ4
and 64-bit ZSTD.

	Before	After ARCH
LZ4	  73ms	 10ms   32
LZ4	 120ms	 10ms	64
ZSTD	  90ms	 74ms	64

Measurements on QEMU on 2.2GHz Broadwell Xeon, using defconfig kernels.

Decompressor code size has small differences, with the largest being
that 64-bit ZSTD decreases just over 2k. The largest code size increase
was on 64-bit XZ, of about 400 bytes.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Suggested-by: Nick Terrell <nickrterrell@gmail.com>
Tested-by: Nick Terrell <nickrterrell@gmail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-19 11:23:45 -07:00
arch x86/boot/compressed: Use builtin mem functions for decompressor 2020-08-19 11:23:45 -07:00
block block-5.9-2020-08-14 2020-08-15 20:36:42 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-08-14 13:09:15 -07:00
Documentation spi: Fixes for v5.9 2020-08-18 14:27:12 -07:00
drivers spi: Fixes for v5.9 2020-08-18 14:27:12 -07:00
fs io_uring-5.9-2020-08-15 2020-08-16 10:55:12 -07:00
include Fix regression in IA-64 caused by page table allocation refactoring 2020-08-18 12:05:46 -07:00
init OpenRISC updates for 5.9 2020-08-14 14:04:53 -07:00
ipc ipc/shm.c: remove the superfluous break 2020-08-12 10:58:02 -07:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-17 17:09:50 -07:00
lib iomap: constify ioreadX() iomem argument (as in generic implementation) 2020-08-14 19:56:57 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm/memory.c: skip spurious TLB flush for retried page fault 2020-08-18 12:02:27 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-17 17:09:50 -07:00
samples Kbuild updates for v5.9 2020-08-09 14:10:26 -07:00
scripts Kconfig updates for v5.9 2020-08-14 11:04:45 -07:00
security Merge branch 'akpm' (patches from Andrew) 2020-08-12 11:24:12 -07:00
sound sound fixes for 5.9-rc1 2020-08-14 15:58:57 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-17 17:09:50 -07:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt Merge branch 'akpm' (patches from Andrew) 2020-08-12 11:24:12 -07:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: Add ZSTD-compressed files 2020-07-31 11:50:49 +02:00
.mailmap mailmap: Add WeiXiong Liao 2020-08-17 14:32:44 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Replace HTTP links with HTTPS ones 2020-07-23 14:53:58 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS perf tools changes for v5.9: 2nd batch 2020-08-15 11:17:15 -07:00
Makefile Linux 5.9-rc1 2020-08-16 13:04:57 -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.