Date: Tue, 13 Mar 2018 19:06:48 +0100
From: Steffen Nurpmeso <steffen@sdaoden.eu>
To: alpine-user@lists.alpinelinux.org
Subject: [alpine-user] FYI: community/zstd binary much (up to 4x) slower than necessary
Message-ID: <20180313180648.kXWsR%steffen@sdaoden.eu>
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BlahBlahBlah: Any stupid boy can crush a beetle. But all the professors in
 the world can make no bugs.
Precedence: list

Hello, for your possible interest.

In a thead for the LUGA(ustria) i eventually had to time some
compression algorithms and wondered why zstd is so slow, but
especially so the decompressing stage, which a key feature of this
one.  It turns out that the -Os compilation causes, well, drama-
tical performance degradation.  I compiled my own with -O3 and the
difference is up to factor four.  Just one example:

POSIX standard (C165.txt):

Alpine, -Os:
  #?0[steffen@essex tmp]$ time zstd --rm x4.txt
  x4.txt               : 20.95%   (12513780 => 2621685 bytes, x4.txt.zst)
      0m00.57s real     0m00.23s user     0m00.12s system
  #?0[steffen@essex tmp]$ time zstd -d -c x4.txt.zst   >/dev/null
  x4.txt.zst          : 12513780 bytes
      0m00.38s real     0m00.15s user     0m00.12s system

  #?0[steffen@essex tmp]$ time zstd --rm -19 x5.txt
  x5.txt               : 15.40%   (12513780 => 1926643 bytes, x5.txt.zst)
      0m16.30s real     0m13.53s user     0m00.27s system

  #?0[steffen@essex tmp]$ time zstd -d -c x5.txt.zst   >/dev/null
  x5.txt.zst          : 12513780 bytes
      0m00.39s real     0m00.12s user     0m00.14s system

-O3:
  #?0[steffen@essex tmp]$ time x/zstd/zstd -f x1.txt
  x1.txt               : 20.95%   (12513780 => 2621685 bytes, x1.txt.zst)
      0m00.34s real     0m00.12s user     0m00.10s system
  #?0[steffen@essex tmp]$ time x/zstd/zstd -d -c x1.txt.zst >/dev/null
  x1.txt.zst          : 12513780 bytes
      0m00.10s real     0m00.02s user     0m00.05s system

  #?0[steffen@essex tmp]$ time x/zstd/zstd -19 x1.txt
  x1.txt               : 15.40%   (12513780 => 1926643 bytes, x1.txt.zst)
      0m13.29s real     0m11.27s user     0m00.17s system
  #?0[steffen@essex tmp]$ time x/zstd/zstd -d -c x1.txt.zst >/dev/null
  x1.txt.zst          : 12513780 bytes
      0m00.12s real     0m00.02s user     0m00.07s system

That makes me actually wonder how ports should deal with CFLAGS.
Is it acceptable for a port to watch for compiler flags and set
them, my MUA would go for PIE, relro and all that, then?

Ciao,

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)


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