[Bug 1812182] Re: Performance degradation with SPECint2017

[Christian Ehrhardt ]

Just to be sure, since Ubuntu's gcc has "--enable-default-pie" I wanted to check.
Do "the others" set pie by default as well?
Just want to make sure that their execution without explicit pie is -no-pie while ours would then be -pie.

For your kernel thoughts - even though the first idea was already falsified by your tests.
You said you are on Kernel 4.4, but the change you mentioned as "maybe related" was in 4.13 and reverted in 4.15.

That said since you suspect the kernel to be related, is in that regard a major difference between?
linux: 4.4.0-141.167
linux-hwe: 4.15.0-43.46~16.04.1

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Title:
  Performance degradation with SPECint2017

Status in Ubuntu on IBM z Systems:
  Incomplete
Status in gcc-5 package in Ubuntu:
  Incomplete
Status in glibc package in Ubuntu:
  Incomplete
Status in linux package in Ubuntu:
  Incomplete

Bug description:
  Problem description:

  During our Linux distribution performance regression testing, we found
  *significant* performance degradations on Ubuntu 16.04.5 LTS compared
  to other major Linux distributions on s390x when running SPECint2017.
  Some SPECint2017 micro-benchmarks show a performance degradation of
  40%.

  Hardware environment:

  IBM z14, LPAR
  1 IFL, SMT on
  4GiB memory

  Software environment:

  Ubuntu 16.04.5 LTS
  SPECint2017

  Analysis:

  We are currently in the progress of analyzing the problem and will get
  back to this bug as soon as we have more insights.

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