Public bug reported:
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?
** Affects: ubuntu
Importance: Undecided
Status: New
** Tags: performance
** Description changed:
I've just upgraded two servers to use 14.10 (they were before at 14.04) and
found that some of 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 not taking
- 519.637u 11.022s 4:42.80 187.6% 0+0k 0+176216io 0pf+0w
+ 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 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.
+ 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 compiliation. Although it is slower (3s vs
+ 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?
** Description changed:
- I've just upgraded two servers to use 14.10 (they were before at 14.04) and
found that some of my builds were taking much longer:
+ 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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https://bugs.launchpad.net/bugs/1388276
Title:
14.10 about 2 to 3 times slower to perform concurrent tasks
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