[Bug 1932010] Comment bridged from LTC Bugzilla

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------- Comment From iii at de.ibm.com 2021-08-11 06:59 EDT-------
zlib1g_1.2.11.dfsg-2ubuntu7~ppa2_s390x.deb works fine, thanks!

# time -p env DFLTCC=0 python3 -c 'import gzip; gzip.decompress(gzip.compress(b"\x00" * 500000000, 1))'
real 2.59
user 2.23
sys 0.35

# dpkg -i zlib1g_1.2.11.dfsg-2ubuntu7~ppa2_s390x.deb

# time -p env DFLTCC=0 python3 -c 'import gzip; gzip.decompress(gzip.compress(b"\x00" * 500000000, 1))'
real 1.99
user 1.62
sys 0.36

However, I'm not quite sure why does

++#ifdef S390_CRC32_VX
++    if (getauxval(AT_HWCAP) & HWCAP_S390_VX)
++        return s390_crc32_vx;
++#endif

work. For me getauxval() causes a segfault when called from an ifunc,
that's why I have to use the s390-specific ifunc's hwcap parameter.

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https://bugs.launchpad.net/bugs/1932010

Title:
  [21.10 FEAT] zlib CRC32 optimization for s390x

Status in Ubuntu on IBM z Systems:
  In Progress
Status in zlib package in Ubuntu:
  In Progress

Bug description:
  Use SIMD instructions to accelerate the zlib CRC32 implementation.
  Business value: Performance improvement in database area

  The zlib CRC32 optimization for IBM Z is currently being discussed for inclusion into zlib-ng:
  https://github.com/zlib-ng/zlib-ng/pull/912

  The patch for zlib will be based on that.

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