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["Christopher M. Penalver" <christopher.m.penalver@xxxxxxxxx>]

** Tags removed: performance
** Tags added: regression-release

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https://bugs.launchpad.net/bugs/1388276

Title:
  14.10 about 2 to 3 times slower to perform concurrent tasks

Status in “linux” package in Ubuntu:
  Incomplete

Bug description:
  I've just upgraded two servers to use 14.10 (they were before at 14.04) and found that my builds were taking much longer:
  - A jenkins regression test suite that took about 135 minutes is now taking about 300 minutes.
  - A C complation tasks  which took the following amount of time (time from tcsh):
   419.633u 9.471s 1:36.78 443.3%  0+0k 0+166968io 0pf+0w
  is now taking
   519.637u 11.022s 4:42.80 187.6% 0+0k 0+176216io 0pf+0w

  Both tasks are heavily using all the available cores of the processor.
  In one case it is a dual socket E5420 ( 8 cores), in another case it
  is a virtualized 8 cores E5645.

  I first thought it could be the new version of gcc (4.9) since both
  tasks involves a lot of C compilation. Although gcc 4.9 is slower (3s
  vs 2.8s in my own tests) it is not enough to explain the difference. I
  actually also tried using gcc 4.8 and 4.7 with the same performance
  degradation.

  I unfortunately do not have a 14.04 server to which I can compare the
  results to see where the difference is in terms of performance.

  Is anyone observing the same behavior?

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