Messages in this thread | | | From | Con Kolivas <> | Subject | Re: [PATCH] O13int for interactivity | Date | Tue, 5 Aug 2003 13:06:38 +1000 |
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On Tue, 5 Aug 2003 12:21, Nick Piggin wrote: > >I've already posted a better solution in O13.1 > > No, this still special-cases the uninterruptible sleep. Why is this > needed? What is being worked around? There is probably a way to > attack the cause of the problem.
Sure I'm open to any and all ideas. Cpu hogs occasionally do significant I/O. Up until that time they have been only losing sleep_avg as they have spent no time sleeping; and this is what gives them a lower dynamic priority. During uninterruptible sleep all of a sudden they are seen as sleeping even though they are cpu hogs waiting on I/O. Witness the old standard, a kernel compile. The very first time you launch a make -j something, the higher the something, the longer all the jobs wait on I/O, the better the dynamic priority they get, which they shouldn't.
No, this is not just a "fix the scheduler so you don't feel -j kernel compiles" as it happens with any cpu hog starving other tasks, and the longer the cpu hogs wait on I/O the worse it is. This change causes a _massive_ improvement for that test case which usually brings the machine to a standstill the size of which is dependent on the number of cpu hogs and the size of their I/O wait. I don't think the latest incarnation should be a problem. In my limited testing I've not found any difference in throughput but I don't have a major testbed at my disposal, nor time to use one if it was offered which is why I requested more testing.
Thoughts?
Con
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