Messages in this thread | | | Date | Thu, 02 Oct 2003 13:05:36 +1000 | From | Nick Piggin <> | Subject | Re: Linux 2.6.0-test6 |
| |
Pedro Larroy wrote:
>On Mon, Sep 29, 2003 at 12:55:12PM -0400, Ed Sweetman wrote: > >>Nick Piggin wrote: >> >>> >>>Rob Landley wrote: >>> >>> >>>>On Sunday 28 September 2003 02:03, Con Kolivas wrote: >>>> >>>> >>>>>On Sun, 28 Sep 2003 11:27, Linus Torvalds wrote: >>>>> >>>>>>from Andrew Morton. Most notably perhaps Con's scheduler changes that >>>>> >>>>>>have been discussed extensively and made it into the -mm tree for >>>>>>testing. >>>>>> >>>>>> >>>>>For those who are trying this for the first time, please note that the >>>>>scheduler has been tuned to tell the difference between tasks of the >>>>>_same_ >>>>>nice level. This means do NOT renice X or it will make audio skip unless >>>>>you also renice your audio application by the same amount. Lots of >>>>>distributions have done this for the old 2.4 scheduler which could not >>>>>treat equal "nice" levels as differently as the new scheduler does >>>>>and 2.6 >>>>>shouldn't need special treatment. >>>>> >>>>>So for testing note the following points: >>>>> >>>>>Make sure X is NOT reniced to -10 as many distributions are doing. >>>>>Some shells spawn processes at nice +5 by default and this will make >>>>>audio >>>>>apps suffer. >>>>>Make sure your hard disk, graphics card and audio card are performing at >>>>>equal standard to your 2.4 kernel (ie dma is working, graphics is fully >>>>>accelerated etc). >>>>> >>>>> >>>>I.E. with your new scheduler, priority levels actually have enough of >>>>an effect now that things that aren't reniced can be noticeably >>>>starved by things that are. >>>> >>>> >>>AFAIK, Con's scheduler doesn't change the nice implementation at all. >>>Possibly some of his changes amplify its problems, or, more likely they >>>remove most other scheduler problems leaving this one noticable. >>> >>>If X is running at -20, and xmms at +19, xmms is supposed to still get >>>5% of the CPU. Should be enough to run fine. Unfortunately this is >>>achieved by giving X very large timeslices, so xmms's scheduling latency >>>becomes large. The interactivity bonuses don't help, either. >>> >>> >>there are 40 positions between -20 and 19, that doesn't equal 5% steps. >>They don't even refer to % of cpu. If i nice a process to -20 it >>doesn't get a given percentage of cpu just because it's -20. I may have >>other processes at -20 as well. If you nice something to -20 and it is >>actually using that cpu then things that are +19 shouldn't run and wont >>run. If I nice -20 vmstat 1, it's not going to starve xmms (or any >>better audio player). -20 means starve all and it should do that when >>it actually makes use of the resources. >> >> > >Why not run xmms with SCHED_RR or SCHED_FIFO? > >
Well because playing an mp3 really is a pitiful task for modern CPUs, and the standard scheduler should handle this fine. Also a music skip isn't terribly important.
Realtime applications are difficult to make robust and they can easily hang the system.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |