linux-kernel - Re: problem with "sched: revert back to per-rq vruntime"?

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Date:	Tue, 30 Dec 2008 13:37:47 -0600
From:	Jayson King <dev@...sonking.com>
To:	linux-kernel@...r.kernel.org
CC:	a.p.zijlstra@...llo.nl, mingo@...e.hu
Subject: Re: problem with "sched: revert back to per-rq vruntime"?

Here's some times using bash, for example. Let me know if there are some 
other tests I can do.

It shows on vanilla 2.6.28, a huge increase in latency (about 37X to 
39X) starting bash -i when the CPU is loaded with 100% nice tasks, 
relative to idle CPU. But after reverting 
f9c0b0950d5fd8c8c5af39bc061f27ea8fddcac3 the latency increase is not as 
great (about 2X).

# running bash -i on vanilla 2.6.28,
# with idle CPU
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.020s
user    0m0.008s
sys     0m0.014s
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.020s
user    0m0.014s
sys     0m0.005s
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.020s
user    0m0.008s
sys     0m0.009s



# running bash -i on vanilla 2.6.28,
# with 100% nice CPU usage
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.753s
user    0m0.011s
sys     0m0.011s
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.752s
user    0m0.012s
sys     0m0.012s
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.786s
user    0m0.010s
sys     0m0.008s



# running 2.6.28 reverted f9c0b0950d5fd8c8c5af39bc061f27ea8fddcac3,
# with idle CPU
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.021s
user    0m0.012s
sys     0m0.007s
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.020s
user    0m0.012s
sys     0m0.011s
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.020s
user    0m0.011s
sys     0m0.012s



# running 2.6.28 reverted f9c0b0950d5fd8c8c5af39bc061f27ea8fddcac3,
# with 100% nice CPU usage
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.043s
user    0m0.010s
sys     0m0.009s
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.046s
user    0m0.011s
sys     0m0.007s
[jayson@...as tmp]$ time bash -i -c 'exit'
exit

real    0m0.047s
user    0m0.011s
sys     0m0.006s




Jayson

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