Messages in this thread | | | Date | Tue, 05 Aug 2003 13:17:51 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH] O13int for interactivity |
| |
Con Kolivas wrote:
>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. >
Well I don't think the scheduler should really care about a process waiting 1 second vs a process waiting 10 seconds. The point of the dynamic priority here is that 1 you want the process to wake up soon to respond to the IO, and 2 you want to give it a bit of an advantage vs a non sleeping CPU hog, right? I think a very rapidly decaying benefit vs sleep time is in order.
> >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? >
Well if it really is the right thing to do, it should be done with _any_ type of sleep, not just uninterruptible. But you may have just answered your question there: "the longer cpu hogs wait on I/O the worse it is". Change the dynamic priority boost so this is no longer the case.
I understand this is essentially what you have done, but you did it in a way that does not allow a task to become "interactive". Try changing the formula used to derive the priority boost?
- 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/
| |