Nick Terrell b1a3e75e46 lz4: fix kernel decompression speed
This patch replaces all memcpy() calls with LZ4_memcpy() which calls
__builtin_memcpy() so the compiler can inline it.

LZ4 relies heavily on memcpy() with a constant size being inlined.  In x86
and i386 pre-boot environments memcpy() cannot be inlined because memcpy()
doesn't get defined as __builtin_memcpy().

An equivalent patch has been applied upstream so that the next import
won't lose this change [1].

I've measured the kernel decompression speed using QEMU before and after
this patch for the x86_64 and i386 architectures.  The speed-up is about
10x as shown below.

Code	Arch	Kernel Size	Time	Speed
v5.8	x86_64	11504832 B	148 ms	 79 MB/s
patch	x86_64	11503872 B	 13 ms	885 MB/s
v5.8	i386	 9621216 B	 91 ms	106 MB/s
patch	i386	 9620224 B	 10 ms	962 MB/s

I also measured the time to decompress the initramfs on x86_64, i386, and
arm.  All three show the same decompression speed before and after, as
expected.

[1] https://github.com/lz4/lz4/pull/890

Signed-off-by: Nick Terrell <terrelln@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Yann Collet <yann.collet.73@gmail.com>
Cc: Gao Xiang <gaoxiang25@huawei.com>
Cc: Sven Schmidt <4sschmid@informatik.uni-hamburg.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Link: http://lkml.kernel.org/r/20200803194022.2966806-1-nickrterrell@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-14 19:56:56 -07:00
..
2020-08-09 14:10:26 -07:00
2020-08-14 19:56:56 -07:00
2020-05-24 20:48:11 +02:00
2018-08-16 12:14:42 -07:00
2020-06-01 08:23:42 -04:00
2014-04-30 19:49:37 +01:00
2017-02-24 17:46:57 -08:00
2020-05-07 14:54:26 +08:00
2020-08-12 10:58:00 -07:00
2018-10-16 13:45:44 +02:00
2020-06-15 18:22:43 -07:00
2019-07-11 15:17:41 -07:00
2018-06-27 18:58:49 +03:00
2020-06-29 10:02:23 +02:00
2018-10-15 16:31:29 -04:00
2020-06-07 10:53:36 -07:00
2020-06-09 10:03:12 -07:00
2020-06-04 19:06:28 -07:00