Re: Linux 2.6.0-test6

[bill davidsen]

In article <3F78D866.5070605@xxxxxxxxxxxxxxx>,
Nick Piggin  <piggin@xxxxxxxxxxxxxxx> wrote:
| 
| 
| bill davidsen wrote:
| 
| >In article <3F77BB2C.7030402@xxxxxxxxxxxxxxx>,
| >Nick Piggin  <piggin@xxxxxxxxxxxxxxx> wrote:
| >
| >| AFAIK, Con's scheduler doesn't change the nice implementation at all.
| >| Possibly some of his changes amplify its problems, or, more likely they
| >| remove most other scheduler problems leaving this one noticable.
| >| 
| >| If X is running at -20, and xmms at +19, xmms is supposed to still get
| >| 5% of the CPU. Should be enough to run fine. Unfortunately this is
| >| achieved by giving X very large timeslices, so xmms's scheduling latency
| >| becomes large. The interactivity bonuses don't help, either.
| >
| >Clearly the "some is good, more is better" approach doesn't provide
| >stable balance between sound and cpu hogs. It isn't a question of "how
| >much" cpu, just "when"which works or not.
| >
| >This is sort of like the deadline scheduler in that it trades of
| >throughput for avoiding jackpot cases. I think that's desired behaviour
| >in a CPU schedular too, at least if used by humans.
| >
| 
| I'm not sure what you mean. There is nothing good to say about Ingo's
| nice mechanism though (sorry Ingo, its otherwise a very nice
| scheduler!).

Oh, I think the test5-mm4 behaviour is far better than yours in terms of
throughput. I would expect that it could have several percent less
system time, leaving it for cpu-bound user processes. However, on my
little test machine (PII-350 w/ 96MB) running patch to get a kernel
source tree ready makes the system damn near unusable. With your v15
patch neither patch nor a kernel build is a real problem (I don't use
-j, there's only one processor and it doesn't help). I can happily read
mail, run windows to remote machines to do admin, check web based
monitors, and generally use the system. It's not a ball of fire, but
it's old and slow moving, and I can identify with that ;-)

| In my scheduler, nice -20 processes get small timeslices so scheduling
| latency stays low or even gets lower, while nice +19 ones get large
| timeslices for lower context switches and better cache efficiency. As
| you would like.

Clearly your timeslices don't get so large the system suffers. And I can
run setiathome with a little nice, like -5, and it will get some time
without slowing the important stuff on the system. Even at -19 it does
keep going. On a small memory machine I hate to give pages to a process
without giving it the CPU to justify the memory.

I'm going to try test5-n15 against test5-mm4 and test6-std with a server
load, but for now I run your patch on machines I use as personal
workstations. I haven't tried it SMP, that day will come.
-- 
bill davidsen <davidsen@xxxxxxx>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.
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