Messages in this thread | | | Date | Tue, 23 Dec 2003 12:11:02 +1100 | From | Nick Piggin <> | Subject | Re: [PATCH] 2.6.0 batch scheduling, HT aware |
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Con Kolivas wrote:
>I've done a resync and update of my batch scheduling that is also hyper-thread >aware. > >What is batch scheduling? Specifying a task as batch allows it to only use cpu >time if there is idle time available, rather than having a proportion of the >cpu time based on niceness. > >Why do I need hyper-thread aware batch scheduling? > >If you have a hyperthread (P4HT) processor and run it as two logical cpus you >can have a very low priority task running that can consume 50% of your >physical cpu's capacity no matter how high priority tasks you are running. >For example if you use the distributed computing client setiathome you will >be effectively be running at half your cpu's speed even if you run setiathome >at nice 20. Batch scheduling for normal cpus allows only idle time to be used >for batch tasks, and for HT cpus only allows idle time when both logical cpus >are idle. > >This is not being pushed for mainline kernel inclusion, but the issue of how >to prevent low priority tasks slowing down HT cpus needs to be considered for >the mainline HT scheduler if it ever gets included. This patch provides a >temporising measure for those with HT processors, and a demonstrative way to >handle them in mainline. >
I wonder how does Intel suggest we handle this problem? Batch scheduling aside, I wonder how to do any sort of priorities at all? I think POWER5 can do priorities in hardware, that is the only sane way I can think of doing it.
I think this patch is much too ugly to get into such an elegant scheduler. No fault to you Con because its an ugly problem.
How about this: if a task is "delta" priority points below a task running on another sibling, move it to that sibling (so priorities via timeslice start working). I call it active unbalancing! I might be able to make it fit if there is interest. Other suggestions?
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