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Bugzilla – Full Text Bug Listing |
| Summary: | CONFIG_HZ=1000 and PREEMPT enabled would be preffered for desktop kernels | ||
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| Product: | [openSUSE] openSUSE 11.1 | Reporter: | Stefan Sauer <ensonic> |
| Component: | Kernel | Assignee: | E-mail List <kernel-maintainers> |
| Status: | RESOLVED WONTFIX | QA Contact: | E-mail List <qa-bugs> |
| Severity: | Enhancement | ||
| Priority: | P5 - None | CC: | chrubis, forgotten_b49zM5D78q, georgmueller, kontakt |
| Version: | Final | ||
| Target Milestone: | --- | ||
| Hardware: | All | ||
| OS: | openSUSE 11.1 | ||
| Whiteboard: | |||
| Found By: | --- | Services Priority: | |
| Business Priority: | Blocker: | --- | |
| Marketing QA Status: | --- | IT Deployment: | --- |
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Description
Stefan Sauer
2009-02-22 19:48:25 UTC
Please also consider to enable: CONFIG_PREEMPT and CONFIG_PREEMPT_VOLUNTARY CONFIG_PREEMPT_NOTIFIERS=y CONFIG_PREEMPT_NONE=y # CONFIG_PREEMPT_VOLUNTARY is not set # CONFIG_PREEMPT is not set http://kernel.xc.net/html/linux-2.6.23/i386/PREEMPT http://kernel.xc.net/html/linux-2.6.23/i386/PREEMPT_VOLUNTARY Example explanation: https://tango.0pointer.de/pipermail/pulseaudio-discuss/2009-February/003150.html Because we share this kernel with servers, we can't change the HZ, it would dramatically decrease our throughput on those workloads. As for any seen latencies, please let us know where they are and we will be glad to work to resolve them. You can try using the latencytop tool to locate them. This is related to bug 461361. For future releases, would it be possible to have a desktop kernel and a server kernel? Can PREEMPT help here without changing the HZ? (In reply to comment #4) > This is related to bug 461361. > > For future releases, would it be possible to have a desktop kernel and a server > kernel? We are taking it under consideration, but in reality, it's better to just fix the latency issues in the specific portions of the kernel that have it than to have two separate kernels. > Can PREEMPT help here without changing the HZ? Not much. Again, if you can help find the places where there is latency, we can fix them. Try using latencytop, that is what it is for. Having separate kernels seems to be a practise followed by different distros. The issue for me is audio. PulseAudio does not work reliably in glich-free mode - latency is way too high. Also the jack audio server is barely useable for me on 11.1. Interestingly jack worked reasonable on 11.0. I am playing with latencytop right now, but I have to figure yet how to interpret the values. This is shown in the upper part: Cause Maximum Percentage ATA/SCSI disk ioctl 77.2 msec 1.9 % Scheduler: waiting for cpu 66.6 msec 28.4 % Executing raw SCSI command 21.7 msec 26.7 % Writing buffer to disk (synchronous) 20.0 msec 0.3 % opening cdrom device 6.4 msec 5.6 % Waiting for event (select) 5.0 msec 16.3 % Waiting for event (poll) 5.0 msec 16.8 % SCSI cdrom ioctl 4.1 msec 1.2 % Userspace lock contention 4.1 msec 2.0 % In the lower part I get no listing for pulseaudio or jack. Dunno if they need to be running for a while. For X I get e.g. this: Process X (5105) Total: 503.9 msec Scheduler: waiting for cpu 5.3 msec 79.8 % Waiting for event (select) 4.9 msec 20.2 % I filed bug 480020 about latency. The output of latencytop was: Cause Maximum Percentage fsync() on a file 110.7 msec 0.5 % Scheduler: waiting for cpu 81.1 msec 45.6 % Writing a page to disk 14.6 msec 0.1 % opening cdrom device 10.0 msec 0.2 % Executing raw SCSI command 5.4 msec 0.2 % Waiting for event (poll) 5.0 msec 15.7 % Waiting for event (select) 5.0 msec 7.7 % Userspace lock contention 5.0 msec 30.0 % Waiting for event (epoll) 4.0 msec 0.1 % Process pulseaudio (2998) Total: 3586.0 msec Scheduler: waiting for cpu 81.1 msec 99.1 % Waiting for event (poll) 4.8 msec 0.9 % Userspace lock contention 0.1 msec 0.0 % |