linux-stable/lib/zstd
Nick Terrell 7416cdc9b9 lib: zstd: Don't add -O3 to cflags
After the update to zstd-1.4.10 passing -O3 is no longer necessary to
get good performance from zstd. Using the default optimization level -O2
is sufficient to get good performance.

I've measured no significant change to compression speed, and a ~1%
decompression speed loss, which is acceptable.

This fixes the reported parisc -Wframe-larger-than=1536 errors [0]. The
gcc-8-hppa-linux-gnu compiler performed very poorly with -O3, generating
stacks that are ~3KB. With -O2 these same functions generate stacks in
the < 100B, completely fixing the problem. Function size deltas are
listed below:

ZSTD_compressBlock_fast_extDict_generic: 3800 -> 68
ZSTD_compressBlock_fast: 2216 -> 40
ZSTD_compressBlock_fast_dictMatchState: 1848 ->  64
ZSTD_compressBlock_doubleFast_extDict_generic: 3744 -> 76
ZSTD_fillDoubleHashTable: 3252 -> 0
ZSTD_compressBlock_doubleFast: 5856 -> 36
ZSTD_compressBlock_doubleFast_dictMatchState: 5380 -> 84
ZSTD_copmressBlock_lazy2: 2420 -> 72

Additionally, this improves the reported code bloat [1]. With gcc-11
bloat-o-meter shows an 80KB code size improvement:

```
> ../scripts/bloat-o-meter vmlinux.old vmlinux
add/remove: 31/8 grow/shrink: 24/155 up/down: 25734/-107924 (-82190)
Total: Before=6418562, After=6336372, chg -1.28%
```

Compared to before the zstd-1.4.10 update we see a total code size
regression of 105KB, down from 374KB at v5.16-rc1:

```
> ../scripts/bloat-o-meter vmlinux.old vmlinux
add/remove: 292/62 grow/shrink: 56/88 up/down: 235009/-127487 (107522)
Total: Before=6228850, After=6336372, chg +1.73%
```

[0] https://lkml.org/lkml/2021/11/15/710
[1] https://lkml.org/lkml/2021/11/14/189

Link: https://lore.kernel.org/r/20211117014949.1169186-4-nickrterrell@gmail.com/
Link: https://lore.kernel.org/r/20211117201459.1194876-4-nickrterrell@gmail.com/

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Nick Terrell <terrelln@fb.com>
2021-11-18 13:16:22 -08:00
..
common lib: zstd: Don't inline functions in zstd_opt.c 2021-11-18 13:15:33 -08:00
compress lib: zstd: Don't inline functions in zstd_opt.c 2021-11-18 13:15:33 -08:00
decompress lib: zstd: Add cast to silence clang's -Wbitwise-instead-of-logical 2021-11-08 16:55:38 -08:00
decompress_sources.h lib: zstd: Upgrade to latest upstream zstd version 1.4.10 2021-11-08 16:55:32 -08:00
Makefile lib: zstd: Don't add -O3 to cflags 2021-11-18 13:16:22 -08:00
zstd_compress_module.c lib: zstd: Upgrade to latest upstream zstd version 1.4.10 2021-11-08 16:55:32 -08:00
zstd_decompress_module.c lib: zstd: Upgrade to latest upstream zstd version 1.4.10 2021-11-08 16:55:32 -08:00