Hi Nick, On Wed, Nov 17, 2021 at 9:08 PM Nick Terrell <nickrterrell@xxxxxxxxx> wrote: > From: Nick Terrell <terrelln@xxxxxx> > > 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 > > Reported-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > Signed-off-by: Nick Terrell <terrelln@xxxxxx> Impact on vmlinux for atari_defconfig: add/remove: 22/3 grow/shrink: 7/91 up/down: 3246/-35548 (-32302) Impact on lib/zstd/zstd_compress.ko for atari_defconfig: add/remove: 63/5 grow/shrink: 23/197 up/down: 13410/-168604 (-155194) Tested-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> Reviewed-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
