Does the kernel scheduler even matter???

Posted Sep 7, 2009 11:05 UTC (Mon) by eru (subscriber, #2753)
In reply to: BFS vs. mainline scheduler benchmarks and measurements by russell
Parent article: BFS vs. mainline scheduler benchmarks and measurements

It seems to me most of the desktop latencies stem from bloated desktop managers and other GUI software, and from bad graphics drivers. The kernel cannot fix these issues, no matter which scheduler it has. The question to ask is do the user interface really have to relay events through about 100 levels of complex libraries every time the user performs some action.

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Does the kernel scheduler even matter???

Posted Sep 7, 2009 11:21 UTC (Mon) by mjthayer (guest, #39183) [Link] (2 responses)

Still, if (and I haven't actually done any tests here) the kernel can fix this in a reasonable way, why not do it?

Does the kernel scheduler even matter???

Posted Sep 7, 2009 13:46 UTC (Mon) by mingo (subscriber, #31122) [Link] (1 responses)

For many things the process scheduler does matter.

For most desktop things, the IO scheduler, the file system and the VM has a far bigger role.

To measure latencies, there's the latencytop tool from Arjan that can give a first-level guess about what the main source of latencies is.

If it's IO latencies then blktrace can be used to pin them down more precisely.

If it's indeed the process scheduler that is causing latencies, the latency tracer can be used to pin down the reason more precisely. On the lowest level the function tracer can be used too, for harder cases. There's also a lot of built-in statistics, tracepoints and in .31 based kernels also performance counters that can help in the pinning down of such bugs.

Does the kernel scheduler even matter???

Posted Sep 10, 2009 20:54 UTC (Thu) by ajb (subscriber, #9694) [Link]

The scheduler could still help more under conditions of VM stress. For example, on my netbook, which thrashes when you run firefox + anything, I literally run killall -STOP firefox-bin; killall -CONT other-app when I want to switch between them. This is a lot more convenient than quitting and restarting each app, which otherwise I would have to do. I imagine there might be some less manual way to achieve the same thing by building some more smarts into the scheduler/VM to achieve the same effect. Possibly with help from userspace.