From b1a3e75e466d96383508634f3d2e477ac45f2fc1 Mon Sep 17 00:00:00 2001 From: Nick Terrell Date: Fri, 14 Aug 2020 17:30:10 -0700 Subject: 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 Signed-off-by: Andrew Morton Cc: Yann Collet Cc: Gao Xiang Cc: Sven Schmidt <4sschmid@informatik.uni-hamburg.de> Cc: Greg Kroah-Hartman Cc: Ingo Molnar Cc: Arvind Sankar Link: http://lkml.kernel.org/r/20200803194022.2966806-1-nickrterrell@gmail.com Signed-off-by: Linus Torvalds --- lib/lz4/lz4_compress.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'lib/lz4/lz4_compress.c') diff --git a/lib/lz4/lz4_compress.c b/lib/lz4/lz4_compress.c index cc7b6d4cc7c7..90bb67994688 100644 --- a/lib/lz4/lz4_compress.c +++ b/lib/lz4/lz4_compress.c @@ -446,7 +446,7 @@ _last_literals: *op++ = (BYTE)(lastRun << ML_BITS); } - memcpy(op, anchor, lastRun); + LZ4_memcpy(op, anchor, lastRun); op += lastRun; } @@ -708,7 +708,7 @@ _last_literals: } else { *op++ = (BYTE)(lastRunSize<