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Christophe Leroy 0a571b085f asm-generic: force inlining of get_order() to work around gcc10 poor decision 
When building mpc885_ads_defconfig with gcc 10.1,
the function get_order() appears 50 times in vmlinux:

  [linux]# ppc-linux-objdump -x vmlinux | grep get_order | wc -l
  50

  [linux]# size vmlinux
     text	   data	    bss	    dec	    hex	filename
  3842620	 675624	 135160	4653404	 47015c	vmlinux

In the old days, marking a function 'static inline' was forcing GCC to
inline, but since commit ac7c3e4ff4 ("compiler: enable
CONFIG_OPTIMIZE_INLINING forcibly") GCC may decide to not inline a
function.

It looks like GCC 10 is taking poor decisions on this.

get_order() compiles into the following tiny function, occupying 20
bytes of text.

  0000007c <get_order>:
    7c:   38 63 ff ff     addi    r3,r3,-1
    80:   54 63 a3 3e     rlwinm  r3,r3,20,12,31
    84:   7c 63 00 34     cntlzw  r3,r3
    88:   20 63 00 20     subfic  r3,r3,32
    8c:   4e 80 00 20     blr

By forcing get_order() to be __always_inline, the size of text is
reduced by 1940 bytes, that is almost twice the space occupied by
50 times get_order()

  [linux-powerpc]# size vmlinux
     text	   data	    bss	    dec	    hex	filename
  3840680	 675588	 135176	4651444	 46f9b4	vmlinux

Link: https://lkml.kernel.org/r/96c6172d619c51acc5c1c4884b80785c59af4102.1602949927.git.christophe.leroy@csgroup.eu
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-12-15 22:46:15 -08:00
arch alpha: replace bogus in_interrupt() 2020-12-15 22:46:15 -08:00
block Scheduler updates: 2020-12-14 18:29:11 -08:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto crypto: aegis128 - avoid spurious references crypto_aegis128_update_simd 2020-12-04 18:16:53 +11:00
Documentation proc: provide details on indirect branch speculation 2020-12-15 22:46:15 -08:00
drivers pci-v5.11-changes 2020-12-15 16:49:59 -08:00
fs fs/proc: make pde_get() return nothing 2020-12-15 22:46:15 -08:00
include asm-generic: force inlining of get_order() to work around gcc10 poor decision 2020-12-15 22:46:15 -08:00
init Merge branch 'akpm' (patches from Andrew) 2020-12-15 12:53:37 -08:00
ipc Merge branch 'akpm' (patches from Andrew) 2020-12-15 12:53:37 -08:00
kernel ACPI updates for 5.11-rc1 2020-12-15 16:39:06 -08:00
lib ACPI updates for 5.11-rc1 2020-12-15 16:39:06 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm mm/memory_hotplug: quieting offline operation 2020-12-15 22:46:15 -08:00
net Networking updates for 5.11 2020-12-15 13:22:29 -08:00
samples samples/bpf: Fix possible hang in xdpsock with multiple threads 2020-12-10 23:13:43 +01:00
scripts Networking updates for 5.11 2020-12-15 13:22:29 -08:00
security Networking updates for 5.11 2020-12-15 13:22:29 -08:00
sound ACPI updates for 5.11-rc1 2020-12-15 16:39:06 -08:00
tools Power management updates for 5.11-rc1 2020-12-15 16:30:31 -08:00
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 kvm: x86/mmu: Support dirty logging for the TDP MMU 2020-10-23 03:42:13 -04:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.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: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-12-11 22:29:38 -08:00
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 pci-v5.11-changes 2020-12-15 16:49:59 -08:00
Makefile Linux 5.10 2020-12-13 14:41:30 -08:00
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.