Messages in this thread | | | Date | Mon, 17 Mar 2008 00:12:39 -0600 | From | Joe Peterson <> | Subject | Interactivity degrades with CONFIG_[FAIR]_GROUP_SCHED set in 2.6.24 and later |
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First of all, I am very excited to see the CFS in the kernel. Interactivity is really great; much better than before.
When going from kernel 2.6.23 to 2.6.24, however, I noticed that interactivity (namely the smoothness of mouse motion) was noticeably less smooth under load. The most obvious case was while pulling down a Subversion repository; the mouse would freeze for quite long periods while being moved (i.e. a large fraction of a second), which never happens under 2.6.23. I was using ZFS-FUSE on the partition I was writing to, and it uses a lot of CPU at times, but 2.6.23 seems to handle it better.
After reading many posts on similar sounding issues, I decided to try getting later versions of the kernel: 2.6.25-rc5 and the latest 2.6.25 from the git archive (as of yesterday, 3/16) in case recent patches addressed this. They both still exibit the issue, however.
I then tried compiling without CONFIG_GROUP_SCHED (which also turned off CONFIG_FAIR_GROUP_SCHED and a number of other options), and the behavior seems to be back to the (better) 2.6.23 performance, at least has far as what I can tell from my tests.
After playing around with the later kernels with CONFIG_GROUP_SCHED enabled, I noticed a number of random times the mouse was not smooth and seemed to not be getting an "interactive" amount of CPU time, but I have a couple of tasks that repeat the problem reliably, so if there is any debug information I can provide, please let me know, and I'll be glad to help out in any way I can.
Thanks, Joe
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