Messages in this thread | | | Date | Wed, 5 Dec 2007 16:40:14 +0100 | From | Ingo Molnar <> | Subject | Re: Possible bug from kernel 2.6.22 and above, 2.6.24-rc4 |
| |
* Jie Chen <chen@jlab.org> wrote:
> I just ran the same test on two 2.6.24-rc4 kernels: one with > CONFIG_FAIR_GROUP_SCHED on and the other with CONFIG_FAIR_GROUP_SCHED > off. The odd behavior I described in my previous e-mails were still > there for both kernels. Let me know If I can be any more help. Thank > you.
ok, i had a look at your data, and i think this is the result of the scheduler balancing out to idle CPUs more agressively than before. Doing that is almost always a good idea though - but indeed it can result in "bad" numbers if all you do is to measure the ping-pong "performance" between two threads. (with no real work done by any of them).
the moment you saturate the system a bit more, the numbers should improve even with such a ping-pong test.
do you have testcode (or a modification of your testcase sourcecode) that simulates a real-life situation where 2.6.24-rc4 performs not as well as you'd like it to see? (or if qmt.tar.gz already contains that then please point me towards that portion of the test and how i should run it - thanks!)
Ingo
| |