crumja
11-30-2008, 01:58 AM
Hey, just thought I'd enumerate a bunch of noted slowdowns in Linux I and other people have discovered. I'm relying on some of the numbers from Ubuntu (mainly due to Phoronix's popular recent articles comparing performance), but I'm sure they apply to other distros just as well.
Having talked to some devs and noting that most of the performance loss is introduced between 7.10 and 8.04, I'm wondering if it's due to the CFS task scheduler introduced in 2.6.23 (http://www.linuxforums.org/forum/linux-kernel/123688-my-program-cannot-get-fair-cpu-time-under-cfs.html) (kernel between 7.10 and 8.04).
Other word on the street (confirmed by my own experiments) is that heavy disk I/O stops all cpu activity on currently running tasks (https://lists.ubuntu.com/archives/ubuntu-devel/2008-October/026817.html). I wonder if it's due to the new I/O scheduler (elevator option at boot). I've heard that using deadline instead of CFQ (http://www.mail-archive.com/ubuntu-devel-discuss@lists.ubuntu.com/msg06088.html) allows responsive multitasking again.
There is also a known regression with the intel open-source video driver (https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/252094) that is resulting in lower and lower performance on 8.04, 8.10, and 9.04 alpha.
The ultimate goal is to question why we are seeing these serious and noticeable performance regressions. Devs don't usually take notice because we don't have enough clout or hard metrics (just lots of anecdotal evidence). Let's band together to solve this.
Having talked to some devs and noting that most of the performance loss is introduced between 7.10 and 8.04, I'm wondering if it's due to the CFS task scheduler introduced in 2.6.23 (http://www.linuxforums.org/forum/linux-kernel/123688-my-program-cannot-get-fair-cpu-time-under-cfs.html) (kernel between 7.10 and 8.04).
Other word on the street (confirmed by my own experiments) is that heavy disk I/O stops all cpu activity on currently running tasks (https://lists.ubuntu.com/archives/ubuntu-devel/2008-October/026817.html). I wonder if it's due to the new I/O scheduler (elevator option at boot). I've heard that using deadline instead of CFQ (http://www.mail-archive.com/ubuntu-devel-discuss@lists.ubuntu.com/msg06088.html) allows responsive multitasking again.
There is also a known regression with the intel open-source video driver (https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/252094) that is resulting in lower and lower performance on 8.04, 8.10, and 9.04 alpha.
The ultimate goal is to question why we are seeing these serious and noticeable performance regressions. Devs don't usually take notice because we don't have enough clout or hard metrics (just lots of anecdotal evidence). Let's band together to solve this.