On Tuesday 24 April 2007 16:36, Ingo Molnar wrote: > So, my point is, the nice level of X for desktop users should not be set > lower than a low limit suggested by that particular scheduler's author. > That limit is scheduler-specific. Con i think recommends a nice level of > -1 for X when using SD [Con, can you confirm?], while my tests show that > if you want you can go as low as -10 under CFS, without any bad > side-effects. (-19 was a bit too much)
Nice 0 as a default for X, but if renicing, nice -10 as the lower limit for X on SD. The reason for that on SD is that the priority of freshly woken up tasks (ie not fully cpu bound) for both nice 0 and nice -10 will still be the same at PRIO 1 (see the prio_matrix). Therefore, there will _not_ be preemption of the nice 0 task and a context switch _unless_ it is already cpu bound and has consumed a certain number of cycles and has been demoted. Contrary to popular belief, it is not universal that a less niced task will preempt its more niced counterpart and depends entirely on implementation of nice. Yes it is true that context switch rate will go up with a reniced X because the conditions that lead to preemption are more likely to be met, but it is definitely not every single wakeup of the reniced X. Alas, again, I am forced to spend as little time as possible at the pc for my health, so expect _very few_ responses via email from me. Luckily SD is in pretty fine shape with version 0.46. -- -ck - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
